Method for reporting channel state information in wireless communication system and device therefor

ABSTRACT

A method for receiving, by a user equipment (UE), a channel state information reference signal (CSI-RS) in a wireless communication system, includes receiving, from a base station, CSI-RS resource configuration information related to a numbering for a plurality of CSI-RS resources through a radio resource control (RRC) signaling, wherein the CSI-RS resource configuration information includes first CSI-RS configuration information and at least one second CSI-RS configuration information; and determining numbers for the plurality of CSI-RS resources based on the received CSI-RS resource configuration, wherein a specific CSI-RS resource among the plurality of CSI-RS resources corresponds to a value configured in the first CSI-RS configuration information, and at least one CSI-RS resource except the specific CSI-RS resource among the plurality of CSI-RS resources corresponds to a value configured in the second CSI-RS configuration information, and wherein the specific CSI-RS resource is a CSI-RS resource related to a lowest number among the plurality of CSI-RS resources.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.15/739,929 filed on Dec. 26, 2017, which is the National Phase of PCTInternational Application No. PCT/KR2016/007448 filed on Jul. 8, 2016,which claims the priority benefit under 35 U.S.C. § 119(e) to U.S.Provisional Application No. 62/190,751 filed on Jul. 10, 2015, and U.S.Provisional Application No. 62/343,017 filed on May 30, 2016, all ofwhich are hereby expressly incorporated by reference into the presentapplication.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a wireless communication system and,more particularly, to a method for reporting channel state information(CSI) on the basis of a reference signal in a user equipment (UE) and adevice therefor.

Discussion of the Related Art

A mobile communication system has been developed to provide a voiceservice, while ensuring the user's activity. However, the mobilecommunication system has expanded a scope to a data service, as well asthe voice service, and currently, explosive increase in traffic hascaused shortage of resource and, as users request higher speed services,a more advanced mobile communication system is required.

The requirements of a next generation mobile communication system arerequired to support acceptance of explosive data traffic, a significantincrease in a data rate per user, acceptance of a significantlyincreased number of connected devices, very low end-to-end latency, andhigh energy efficiency. To this end, various technologies such asdual-connectivity, massive multiple input multiple output (MIMO),in-band full duplex, non-orthogonal multiple access (NOMA), support ofsuper-wideband, device networking, and the like, have been researched.

In the current LTE(-A) system, only CSI-RS patterns (or CSI-RSresources) for 1, 2, 4, or 8 ports exist and all have a form of power of2.

However, in case where the number of antennas is large in a transmitter(or a transmitting device) like a massive MIMO system, the CSI-RSpattern may have various forms, and an antennas configuration may bedifferent even for the same number of antennas.

Considering the structure of the transmitting antenna having varioussizes and various patterns, it may be inefficient to limit the number ofCSI-RS ports to only the power of 2.

SUMMARY OF THE INVENTION

An aspect of the present invention provides a method for designing a newCSI-RS pattern or a new CSI-RS resource using antenna ports greater than8 ports in a massive MIMO system.

Another aspect of the present invention provides a rule for antenna portnumbering in each CSI-RS resource in a plurality of CSI-RS resources.

Another aspect of the present invention provides a method for mappingCSI-RS configuration information transmitted through higher layersignaling and CSI-RS resources.

Technical subjects obtainable from the present invention are non-limitedby the above-mentioned technical task. And, other unmentioned technicaltasks may be clearly understood from the following description by thosehaving ordinary skill in the technical field to which the presentinvention pertains.

According to an aspect of the present invention, there is provided amethod for reporting channel state information (CSI), by a userequipment (UE), in a wireless communication system, including:receiving, from a base station (BS), CSI reference signal (RS) resourceconfiguration information indicating resource configuration of a CSI-RSusing antenna ports greater than 8 ports, resources of the CSI-RS usingthe antenna ports greater than 8 ports being configured throughaggregation of two or more legacy CSI-RS resources and the two or morelegacy CSI-RS resources indicating resources of CSI-RS using antennaports less than 8 ports; receiving, from the BS, the CSI-RS usingantenna ports greater than 8 ports on the basis of the received CSI-RSresource configuration information; and reporting, to the BS, the CSI onthe basis of the received CSI-RS.

Also, in this disclosure, the CSI-RS resource configuration informationmay include a plurality of legacy CSI-RS configuration values, and theplurality of legacy CSI-RS configuration values may correspond to thetwo or more aggregated legacy CSI-RS resources, respectively.

Also, in this disclosure, the legacy CSI-RS configuration value may be avalue indicating a positions of a resource element in which the legacyCSI-RS resource starts.

Also, in this disclosure, a specific legacy CSI-RS configuration valueincluded in the CSI-RS resource configuration information may correspondto a legacy CSI-RS resource having a lowest index or correspond to alegacy CSI-RS resource having a highest index, among the aggregatedlegacy CSI-RS resources.

Also, in this disclosure, a first legacy CSI-RS configuration valueincluded in the CSI-RS resource configuration information may correspondto a legacy CSI-RS resource having a lowest index among the aggregatedlegacy CSI-RS resources, and a second legacy CSI-RS configuration valueincluded in the CSI-RS resource configuration information may correspondto a legacy CSI-RS resource having a second lowest index among theaggregated legacy CSI-RS resources.

Also, in this disclosure, the resources of the CSI-RS using antennaports greater than 8 ports may be included in a predetermined number ofcontiguous symbols.

Also, in this disclosure, mapping of antenna port numbers by resourceelements in the legacy CSI-RS resources may be performed according to apredetermined rule.

Also, in this disclosure, the predetermined rule may be sequentiallymapping by legacy CSI-RS resources or sequentially mapping by specificresource elements within each legacy CSI-RS resource.

Also, in this disclosure, the two or more aggregated legacy CSI-RSresources may sequentially correspond to the plurality of legacyconfiguration values, starting from a lowest value or starting from ahighest value.

Also, in this disclosure, the two or more aggregated legacy CSI-RSresources may be 3 or 2 resources.

Also, in this disclosure, the antenna ports greater than the 8 ports maybe 12 ports or 16 ports.

Also, in this disclosure, the antenna ports less than 8 ports may be 1port, 2 ports, 4 ports, or 8 ports.

Also, in this disclosure, the two or more legacy CSI-RS resources may beCSI-RS resource #1, CSI-RS resource #2, and CSI-RS resource #3, andresource elements of the CSI-RS resource #1 may be mapped to antennaports 15, 16, 17, and 18, resource elements of the CSI-RS resource #2may be mapped to antenna ports 19, 20, 21, and 22, and resource elementsof the CSI-RS resource #3 may be mapped to antenna ports 23, 24, 25, and26.

Also, in this disclosure, the two or more legacy CSI-RS resources may beCSI-RS resource #1 and CSI-RS resource #2, and resource elements of theCSI-RS resource #1 may be mapped to antenna ports 15, 16, 17, 18, 19,20, 21, and 22 and resource elements of the CSI-RS resource #2 may bemapped to antenna ports 23, 24, 25, 26, 27, 28, 29, and 30.

Also, in this disclosure, the CSI-RS resource configuration informationmay be received from the BS through higher layer signaling.

Also, in this disclosure, the resources of the CSI-RS using antennaports greater than 8 ports may be included in the same subframe.

According to another aspect of the present invention, there is provideda user equipment (UE) for reporting channel state information (CSI) in awireless communication system, including: a radio frequency (RF) unittransmitting and receiving a radio signal; and a processor controllingthe RF unit, wherein the processor performs control to receive, from abase station (BS), CSI reference signal (RS) resource configurationinformation indicating resource configuration of a CSI-RS using antennaports greater than 8 ports, wherein resources of the CSI-RS using theantenna ports greater than 8 ports are configured through aggregation oftwo or more legacy CSI-RS resources and the two or more legacy CSI-RSresources indicate resources of CSI-RS using antenna ports less than 8ports; receive, from the BS, the CSI-RS using antenna ports greater than8 ports on the basis of the received CSI-RS resource configurationinformation; and report, to the BS, the CSI on the basis of the receivedCSI-RS.

The present disclosure has an effect of maintaining compatibility with alegacy system, as well as efficiently supporting a system having a largenumber of antennas in a transmitter, such as a massive MIMO system, bysetting a new CSI-RS resource by aggregating legacy CSI-RS resources.

Also, the present disclosure has an effect of solving ambiguity betweena UE and a BS by defining an accurate mapping relation with the CSI-RSresource for a CSI-RS configuration transmitted and received through theRRC signaling.

It will be appreciated by persons skilled in the art that that theeffects that could be achieved with the present invention are notlimited to what has been particularly described hereinabove and otheradvantages of the present invention will be more clearly understood by aperson skilled in the art to which the present invention pertains, fromthe following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention.

FIG. 1 shows the structure of a radio frame in a wireless communicationsystem to which an embodiment of the present invention may be applied.

FIG. 2 is a diagram illustrating a resource grid for one downlink slotin a wireless communication system to which an embodiment of the presentinvention may be applied.

FIG. 3 shows the structure of a downlink subframe in a wirelesscommunication system to which an embodiment of the present invention maybe applied.

FIG. 4 shows the structure of an uplink subframe in a wirelesscommunication system to which an embodiment of the present invention maybe applied.

FIG. 5 shows a configuration of a general multi-input multi-output(MIMO) communication system.

FIG. 6 shows channels from multiple transmission antennas to onereception antenna.

FIG. 7 shows an example of component carriers and carrier aggregation ina wireless communication system to which an embodiment of the presentinvention may be applied.

FIG. 8 shows a contention-based random access procedure in a wirelesscommunication system to which an embodiment of the present invention maybe applied.

FIG. 9 shows patterns of reference signals mapped to down link resourceblock pairs in a wireless communication system to which an embodiment ofthe present invention may be applied.

FIG. 10 shows a configuration of a CSI-RS in a wireless communicationsystem to which an embodiment of the present invention may be applied.

FIG. 11 shows an example of a 2D active antenna system having 64 antennaelements to which an embodiment of the present invention may be applied.

FIG. 12 shows a system in which a base station (BS) (or eNB) or aterminal (or UE) has multiple transmission/reception antennas capable offorming an AAS-based 3 dimensional (3D) beam in a wireless communicationsystem to which an embodiment of the present invention may be applied.

FIG. 13 shows an example of a polarization-based 2D planar antenna arraymodel.

FIG. 14 shows an example of a model of transceiver units (TXRUs).

FIG. 15 shows an example of 8 port-CSI-RS resource mapping pattern towhich a method proposed in this disclosure may be applied.

FIG. 16 shows another example of CSI-RS resources to which a methodproposed in this disclosure may be applied.

FIG. 17 shows an example of a 12-port CSI-RS resource structure proposedin this disclosure.

FIG. 18 shows examples of a 2D antenna array model to which a methodproposed in this disclosure may be applied.

FIG. 19 shows another example of a 12-port CSI-RS resource mappingpattern proposed in this disclosure.

FIG. 20 shows another example of a 12-port CSI-RS resource mappingpattern proposed in this disclosure.

FIGS. 21 and 22 show examples of a 16-port CSI-RS pattern proposed inthis disclosure.

FIG. 23 is a view illustrating another example of a 8-port CSI-RSpattern proposed in this disclosure.

FIG. 24 shows an example of various CSI-RS patterns proposed in thisdisclosure.

FIG. 25 is a flow chart illustrating an example of a method forreporting channel state information using aggregated CSI-RS resourcesproposed in this disclosure.

FIG. 26 is a block diagram of a wireless communication device accordingto an embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereafter, preferred embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings. Adetailed description to be disclosed hereinbelow together with theaccompanying drawing is to describe embodiments of the present inventionand not to describe a unique embodiment for carrying out the presentinvention. The detailed description below includes details in order toprovide a complete understanding. However, those skilled in the art knowthat the present invention may be carried out without the details.

In some cases, in order to prevent a concept of the present inventionfrom being ambiguous, known structures and devices may be omitted or maybe illustrated in a block diagram format based on core function of eachstructure and device.

In the specification, a base station means a terminal node of a networkdirectly performing communication with a terminal. In the presentdocument, specific operations described to be performed by the basestation may be performed by an upper node of the base station in somecases. That is, it is apparent that in the network constituted bymultiple network nodes including the base station, various operationsperformed for communication with the terminal may be performed by thebase station or other network nodes other than the base station. A basestation (BS) may be generally substituted with terms such as a fixedstation, Node B, evolved-NodeB (eNB), a base transceiver system (BTS),an access point (AP), and the like. Further, a ‘terminal’ may be fixedor movable and be substituted with terms such as user equipment (UE), amobile station (MS), a user terminal (UT), a mobile subscriber station(MSS), a subscriber station (SS), an advanced mobile station (AMS), awireless terminal (WT), a Machine-Type Communication (MTC) device, aMachine-to-Machine (M2M) device, a Device-to-Device (D2D) device, andthe like.

Hereinafter, a downlink means communication from the base station to theterminal and an uplink means communication from the terminal to the basestation. In the downlink, a transmitter may be a part of the basestation and a receiver may be a part of the terminal. In the uplink, thetransmitter may be a part of the terminal and the receiver may be a partof the base station.

Specific terms used in the following description are provided to helpappreciating the present invention and the use of the specific terms maybe modified into other forms within the scope without departing from thetechnical spirit of the present invention.

The following technology may be used in various wireless access systems,such as code division multiple access (CDMA), frequency divisionmultiple access (FDMA), time division multiple access (TDMA), orthogonalfrequency division multiple access (OFDMA), single carrier-FDMA(SC-FDMA), non-orthogonal multiple access (NOMA), and the like. The CDMAmay be implemented by radio technology universal terrestrial radioaccess (UTRA) or CDMA2000. The TDMA may be implemented by radiotechnology such as Global System for Mobile communications (GSM)/GeneralPacket Radio Service (GPRS)/Enhanced Data Rates for GSM Evolution(EDGE). The OFDMA may be implemented as radio technology such as IEEE802.11(Wi-Fi), IEEE 802.16(WiMAX), IEEE 802-20, E-UTRA (Evolved UTRA),and the like. The UTRA is a part of a universal mobile telecommunicationsystem (UMTS). 3rd generation partnership project (3GPP) long termevolution (LTE) as a part of an evolved UMTS (E-UMTS) using evolved-UMTSterrestrial radio access (E-UTRA) adopts the OFDMA in a downlink and theSC-FDMA in an uplink. LTE-advanced (A) is an evolution of the 3GPP LTE.

The embodiments of the present invention may be based on standarddocuments disclosed in at least one of IEEE 802, 3GPP, and 3GPP2 whichare the wireless access systems. That is, steps or parts which are notdescribed to definitely show the technical spirit of the presentinvention among the embodiments of the present invention may be based onthe documents. Further, all terms disclosed in the document may bedescribed by the standard document.

3GPP LTE/LTE-A is primarily described for clear description, buttechnical features of the present invention are not limited thereto.

General wireless communication system to which an embodiment of thepresent invention may be applied

FIG. 1 shows the structure of a radio frame in a wireless communicationsystem to which an embodiment of the present invention may be applied.

3GPP LTE/LTE-A support a type 1 radio frame structure capable of beingapplied to frequency division duplex (FDD) and a type 2 radio framestructure capable of being applied to time division duplex (TDD).

In FIG. 1, the size of the radio frame in a time domain is expressed ina multiple of a time unit “T_s=1/(15000*2048).” Downlink and uplinktransmission includes a radio frame having an interval ofT_f=307200*T_s=10 ms.

FIG. 1(a) illustrates the type 1 radio frame structure. The type 1 radioframe may be applied to both full duplex FDD and half duplex FDD.

The radio frame includes 10 subframes. One radio frame includes 20 slotseach having a length of T_slot=15360*T_s=0.5 ms. Indices 0 to 19 areassigned to the respective slots. One subframe includes two contiguousslots in the time domain, and a subframe i includes a slot 2i and a slot2i+1. The time taken to send one subframe is called a transmission timeinterval (TTI). For example, the length of one subframe may be 1 ms, andthe length of one slot may be 0.5 ms.

In FDD, uplink transmission and downlink transmission are classified inthe frequency domain. There is no restriction to full duplex FDD,whereas a UE is unable to perform transmission and reception at the sametime in a half duplex FDD operation.

One slot includes a plurality of orthogonal frequency divisionmultiplexing (OFDM) symbols in the time domain and includes a pluralityof resource blocks (RBs) in the frequency domain. An OFDM symbol is forexpressing one symbol period because 3GPP LTE uses OFDMA in downlink.The OFDM symbol may also be called an SC-FDMA symbol or a symbol period.The resource block is a resource allocation unit and includes aplurality of contiguous subcarriers in one slot.

FIG. 1(b) shows the type 2 radio frame structure.

The type 2 radio frame structure includes 2 half frames each having alength of 153600*T_s=5 ms. Each of the half frames includes 5 subframeseach having a length of 30720*T_s=1 ms.

In the type 2 radio frame structure of a TDD system, an uplink-downlinkconfiguration is a rule showing how uplink and downlink are allocated(or reserved) with respect to all of subframes.

Table 1 shows the uplink-downlink configuration.

TABLE 1 Downlink- to-Uplink Uplink- Switch- Downlink point Subframenumber configuration periodicity 0 1 2 3 4 5 6 7 8 9 0 5 ms D S U U U DS U U U 1 5 ms D S U U D D S U U D 2 5 ms D S U D D D S U D D 3 10 ms  DS U U U D D D D D 4 10 ms  D S U U D D D D D D 5 10 ms  D S U D D D D DD D 6 5 ms D S U U U D S U U D

Referring to Table 1, “D” indicates a subframe for downlinktransmission, “U” indicates a subframe for uplink transmission, and “S”indicates a special subframe including the three fields of a downlinkpilot time slot (DwPTS), a guard period (GP), and an uplink pilot timeslot (UpPTS) for each of the subframes of the radio frame.

The DwPTS is used for initial cell search, synchronization or channelestimation by a UE. The UpPTS is used for an eNB to perform channelestimation and for a UE to perform uplink transmission synchronization.The GP is an interval for removing interference occurring in uplink dueto the multi-path delay of a downlink signal between uplink anddownlink.

Each subframe i includes the slot 2i and the slot 2i+1 each having“T_slot=15360*T_s=0.5 ms.”

The uplink-downlink configuration may be divided into seven types. Thelocation and/or number of downlink subframes, special subframes, anduplink subframes are different in the seven types.

A point of time changed from downlink to uplink or a point of timechanged from uplink to downlink is called a switching point.Switch-point periodicity means a cycle in which a form in which anuplink subframe and a downlink subframe switch is repeated in the samemanner. The switch-point periodicity supports both 5 ms and 10 ms. Inthe case of a cycle of the 5 ms downlink-uplink switching point, thespecial subframe S is present in each half frame. In the case of thecycle of the 5 ms downlink-uplink switching point, the special subframeS is present only in the first half frame.

In all of the seven configurations, No. 0 and No. 5 subframes and DwPTSsare an interval for only downlink transmission. The UpPTSs, thesubframes, and a subframe subsequent to the subframes are always aninterval for uplink transmission.

Both an eNB and a UE may be aware of such uplink-downlink configurationsas system information. The eNB may notify the UE of a change in theuplink-downlink allocation state of a radio frame by sending only theindex of configuration information whenever uplink-downlinkconfiguration information is changed. Furthermore, the configurationinformation is a kind of downlink control information. Like schedulinginformation, the configuration information may be transmitted through aphysical downlink control channel (PDCCH) and may be transmitted to allof UEs within a cell in common through a broadcast channel as broadcastinformation.

Table 2 shows a configuration (i.e., the length of a DwPTS/GP/UpPTS) ofthe special subframe.

TABLE 2 Normal cyclic prefix in downlink Extended cyclic prefix in UpPTSdownlink Normal UpPTS cyclic Extended Normal Extended Special prefixcyclic cyclic cyclic subframe in prefix prefix in prefix inconfiguration DwPTS uplink in uplink DwPTS uplink uplink 0  6592 · T_(s)2192 · T_(s) 2560 · T_(s)  7680 · T_(s) 2192 · T_(s) 2560 · T_(s) 119760 · T_(s) 20480 · T_(s) 2 21952 · T_(s) 23040 · T_(s) 3 24144 ·T_(s) 25600 · T_(s) 4 26336 · T_(s)  7680 · T_(s) 4384 · T_(s) 5120 ·T_(s) 5  6592 · T_(s) 4384 · T_(s) 5120 · T_(s) 20480 · T_(s) 6 19760 ·T_(s) 23040 · T_(s) 7 21952 · T_(s) — — — 8 24144 · T_(s) — — —

The structure of the radio frame according to the example of FIG. 1 isonly one example. The number of subcarriers included in one radio frame,the number of slots included in one subframe, and the number of OFDMsymbols included in one slot may be changed in various manners.

FIG. 2 is a diagram illustrating a resource grid for one downlink slotin the wireless communication system to which the present invention maybe applied.

Referring to FIG. 2, one downlink slot includes the plurality of OFDMsymbols in the time domain. Herein, it is exemplarily described that onedownlink slot includes 7 OFDM symbols and one resource block includes 12subcarriers in the frequency domain, but the present invention is notlimited thereto.

Each element on the resource grid is referred to as a resource elementand one resource block includes 12×7 resource elements. The number ofresource blocks included in the downlink slot, NDL is subordinated to adownlink transmission bandwidth.

A structure of the uplink slot may be the same as that of the downlinkslot.

FIG. 3 illustrates a structure of a downlink subframe in the wirelesscommunication system to which the present invention may be applied.

Referring to FIG. 3, a maximum of three former OFDM symbols in the firstslot of the sub frame is a control region to which control channels areallocated and residual OFDM symbols is a data region to which a physicaldownlink shared channel (PDSCH) is allocated. Examples of the downlinkcontrol channel used in the 3GPP LTE include a Physical Control FormatIndicator Channel (PCFICH), a Physical Downlink Control Channel (PDCCH),a Physical Hybrid-ARQ Indicator Channel (PHICH), and the like.

The PFCICH is transmitted in the first OFDM symbol of the subframe andtransports information on the number (that is, the size of the controlregion) of OFDM symbols used for transmitting the control channels inthe subframe. The PHICH which is a response channel to the uplinktransports an Acknowledgement (ACK)/Not-Acknowledgement (NACK) signalfor a hybrid automatic repeat request (HARQ). Control informationtransmitted through a PDCCH is referred to as downlink controlinformation (DCI). The downlink control information includes uplinkresource allocation information, downlink resource allocationinformation, or an uplink transmission (Tx) power control command for apredetermined terminal group.

The PDCCH may transport A resource allocation and transmission format(also referred to as a downlink grant) of a downlink shared channel(DL-SCH), resource allocation information (also referred to as an uplinkgrant) of an uplink shared channel (UL-SCH), paging information in apaging channel (PCH), system information in the DL-SCH, resourceallocation for an upper-layer control message such as a random accessresponse transmitted in the PDSCH, an aggregate of transmission powercontrol commands for individual terminals in the predetermined terminalgroup, a voice over IP (VoIP). A plurality of PDCCHs may be transmittedin the control region and the terminal may monitor the plurality ofPDCCHs. The PDCCH is constituted by one or an aggregate of a pluralityof continuous control channel elements (CCEs). The CCE is a logicalallocation wise used to provide a coding rate depending on a state of aradio channel to the PDCCH. The CCEs correspond to a plurality ofresource element groups. A format of the PDCCH and a bit number ofusable PDCCH are determined according to an association between thenumber of CCEs and the coding rate provided by the CCEs.

The base station determines the PDCCH format according to the DCI to betransmitted and attaches the control information to a cyclic redundancycheck (CRC) to the control information. The CRC is masked with a uniqueidentifier (referred to as a radio network temporary identifier (RNTI))according to an owner or a purpose of the PDCCH. In the case of a PDCCHfor a specific terminal, the unique identifier of the terminal, forexample, a cell-RNTI (C-RNTI) may be masked with the CRC. Alternatively,in the case of a PDCCH for the paging message, a paging indicationidentifier, for example, the CRC may be masked with a paging-RNTI(P-RNTI). In the case of a PDCCH for the system information, in moredetail, a system information block (SIB), the CRC may be masked with asystem information identifier, that is, a system information (SI)-RNTI.The CRC may be masked with a random access (RA)-RNTI in order toindicate the random access response which is a response to transmissionof a random access preamble.

AN enhanced PDCCH (EPDCCH) carries UE-specific signaling. The EPDCCH islocated in a physical resource block (PRB) that is set to be terminalspecific. In other words, as described above, the PDCCH can betransmitted in up to three OFDM symbols in the first slot in thesubframe, but the EPDCCH can be transmitted in the resource region otherthan the PDCCH. The time (i.e., symbol) at which the EPDCCH in thesubframe starts can be set in the UE through higher layer signaling(e.g., RRC signaling, etc.).

The EPDCCH is a resource allocation (DL) associated with the DL-SCHrelated to the transport format, resource allocation and HARQinformation, transmission format associated with the UL-SCH, resourceallocation and HARQ information, SL-SCH (Sidelink Shared Channel), andPSCCH Information, and so on. Multiple EPDCCHs may be supported and theterminal may monitor the set of EPCCHs.

The EPDCCH can be transmitted using one or more successive advanced CCEs(ECCEs), and the number of ECCEs per EPDCCH can be determined for eachEPDCCH format.

Each ECCE can be composed of a plurality of enhanced resource elementgroups (EREGs). EREG is used to define the mapping of ECCEs to REs.There are 16 EREGs per PRB pair. All REs are numbered from 0 to 15 inthe order in which the frequency increases, except for the RE carryingthe DMRS in each PRB pair.

The UE can monitor a plurality of EPDCCHs. For example, one or twoEPDCCH sets may be set in one PRB pair in which the terminal monitorsthe EPDCCH transmission.

A different coding rate for the EPOCH can be realized by mergingdifferent numbers of ECCEs. The EPOCH may use localized transmission ordistributed transmission so that the mapping of the ECCE to the RE inthe PRB may vary.

FIG. 4 illustrates a structure of an uplink subframe in the wirelesscommunication system to which the present invention may be applied.

Referring to FIG. 4, the uplink subframe may be divided into the controlregion and the data region in a frequency domain. A physical uplinkcontrol channel (PUCCH) transporting uplink control information isallocated to the control region. A physical uplink shared channel(PUSCH) transporting user data is allocated to the data region. Oneterminal does not simultaneously transmit the PUCCH and the PUSCH inorder to maintain a single carrier characteristic.

A resource block (RB) pair in the subframe are allocated to the PUCCHfor one terminal. RBs included in the RB pair occupy differentsubcarriers in two slots, respectively. The RB pair allocated to thePUCCH frequency-hops in a slot boundary.

Multi-Input Multi-Output (MIMO)

An MIMO technology uses multiple transmitting (Tx) antennas and multiplereceiving (Rx) antennas by breaking from generally one transmittingantenna and one receiving antenna up to now. In other words, the MIMOtechnology is a technology for achieving capacity increment orcapability enhancement by using a multiple input multiple output antennaat a transmitter side or a receiver side of the wireless communicationsystem. Hereinafter, “MIMO” will be referred to as “multiple inputmultiple output antenna”.

More specifically, the MIMO technology does not depend on one antennapath in order to receive one total message and completes total data bycollecting a plurality of data pieces received through multipleantennas. Consequently, the MIMO technology may increase a data transferrate within in a specific system range and further, increase the systemrange through a specific data transfer rate.

In next-generation mobile communication, since a still higher datatransfer rate than the existing mobile communication is required, it isanticipated that an efficient multiple input multiple output technologyis particularly required. In such a situation, an MIMO communicationtechnology is a next-generation mobile communication technology whichmay be widely used in a mobile communication terminal and a relay andattracts a concern as a technology to overcome a limit of a transmissionamount of another mobile communication according to a limit situationdue to data communication extension, and the like.

Meanwhile, the multiple input multiple output (MIMO) technology amongvarious transmission efficiency improvement technologies which have beenresearched in recent years as a method that may epochally improve acommunication capacity and transmission and reception performancewithout additional frequency allocation or power increment has thelargest attention in recent years.

FIG. 5 is a configuration diagram of a general multiple input multipleoutput (MIMO) communication system.

Referring to FIG. 5, when the number of transmitting antennas increasesto NT and the number of receiving antennas increases to NR at the sametime, since a theoretical channel transmission capacity increases inproportion to the number of antennas unlike a case using multipleantennas only in a transmitter or a receiver, a transfer rate may beimproved and frequency efficiency may be epochally improved. In thiscase, the transfer rate depending on an increase in channel transmissioncapacity may theoretically increase to a value acquired by multiplying amaximum transfer rate (Ro) in the case using one antenna by a rateincrease rate (Ri) given below.

R _(i)=min(N _(T) ,N _(R))  [Equation 1]

That is, for example, in an MIMO communication system using fourtransmitting antennas and four receiving antennas, a transfer rate whichis four times higher than a single antenna system may be acquired.

Such an MIMO antenna technology may be divided into a spatial diversityscheme increasing transmission reliability by using symbols passingthrough various channel paths and a spatial multiplexing schemeimproving the transfer rate by simultaneously transmitting multiple datasymbols by using multiple transmitting antennas. Further, a researchinto a scheme that intends to appropriately acquire respectiveadvantages by appropriately combining two schemes is also a field whichhas been researched in recent years.

The respective schemes will be described below in more detail.

First, the spatial diversity scheme includes a space-time block codingseries and a space-time Trelis coding series scheme simultaneously usinga diversity gain and a coding gain. In general, the Trelis is excellentin bit error rate enhancement performance and code generation degree offreedom, but the space-time block code is simple in operationalcomplexity. In the case of such a spatial diversity gain, an amountcorresponding to a multiple (NT×NR) of the number (NT) of transmittingantennas and the number (NR) of receiving antennas may be acquired.

Second, the spatial multiplexing technique is a method that transmitsdifferent data arrays in the respective transmitting antennas and inthis case, mutual interference occurs among data simultaneouslytransmitted from the transmitter in the receiver. The receiver receivesthe data after removing the interference by using an appropriate signalprocessing technique. A noise removing scheme used herein includes amaximum likelihood detection (MLD) receiver, a zero-forcing (ZF)receiver, a minimum mean square error (MMSE) receiver, a diagonal-belllaboratories layered space-time (D-BLAST), a vertical-bell laboratorieslayered space-time), and the like and in particular, when channelinformation may be known in the transmitter side, a singular valuedecomposition (SVD) scheme, and the like may be used.

Third, a technique combining the space diversity and the spatialmultiplexing may be provided. When only the spatial diversity gain isacquired, the performance enhancement gain depending on an increase indiversity degree is gradually saturated and when only the spatialmultiplexing gain is acquired, the transmission reliability deterioratesin the radio channel. Schemes that acquire both two gains while solvingthe problem have been researched and the schemes include a space-timeblock code (Double-STTD), a space-time BICM (STBICM), and the like.

In order to describe a communication method in the MIMO antenna systemdescribed above by a more detailed method, when the communication methodis mathematically modeled, the mathematical modeling may be shown asbelow.

First, it is assumed that NT transmitting antennas and NR receivingantennas are present as illustrated in FIG. 5.

First, in respect to a transmission signal, when NT transmittingantennas are provided, NT may be expressed as a vector given belowbecause the maximum number of transmittable information is NT.

s=└s ₁ ,s ₂ ,Λ,s _(N) _(T) ┘^(T)  [Equation 2]

Transmission power may be different in the respective transmissioninformation s1, s2, . . . , sNT and in this case, when the respectivetransmission power is P1, P2, . . . , PNT, the transmission informationof which the transmission power is adjusted may be expressed as a vectorgiven below.

ŝ=[ŝ ₁ ,ŝ ₂ ,Λ,ŝ _(N) _(T) ]^(T)=[P ₁ s ₁ ,P ₂ s ₂ ,Λ,P _(N) _(T) s _(N)_(T) ]^(T)  [Equation 3]

Further, ŝ may be expressed as described below as a diagonal matrix P ofthe transmission power.

$\begin{matrix}{\hat{s} = {{\begin{bmatrix}P_{1} & \mspace{11mu} & \; & 0 \\\; & P_{2} & \; & \; \\\; & \; & O & \; \\0 & \; & \; & P_{N_{T}}\end{bmatrix}\begin{bmatrix}s_{1} \\s_{2} \\M \\s_{N_{T}}\end{bmatrix}} = {Ps}}} & \left\lbrack {{Equation}\mspace{14mu} 4} \right\rbrack\end{matrix}$

The information vector ŝ of which the transmission power is adjusted ismultiplied by a weight matrix W to constitute NT transmission signalsx1, x2, . . . , xNT which are actually transmitted. Herein, the weightmatrix serves to appropriately distribute the transmission informationto the respective antennas according to a transmission channelsituation, and the like. The transmission signals x1, x2, . . . , xNTmay be expressed as below by using a vector x.

$\begin{matrix}{x = {\quad{\begin{bmatrix}x_{1} \\x_{2} \\M \\x_{i} \\M \\x_{N_{T}}\end{bmatrix} = {{\begin{bmatrix}w_{11} & w_{12} & \Lambda & w_{1N_{T}} \\w_{21} & w_{22} & \Lambda & w_{2N_{T}} \\M & \; & O & \; \\w_{i\; 1} & w_{i\; 2} & \Lambda & w_{{iN}_{T}} \\M & \; & O & \; \\w_{N_{T}1} & w_{N_{T}2} & \Lambda & w_{N_{T}N_{T}}\end{bmatrix}\begin{bmatrix}{\hat{s}}_{1} \\{\hat{s}}_{2} \\M \\{\hat{s}}_{j} \\M \\{\hat{s}}_{N_{T}}\end{bmatrix}} = {{W\hat{s}} = {WPs}}}}}} & \left\lbrack {{Equation}\mspace{14mu} 5} \right\rbrack\end{matrix}$

In Equation 5, wij represents a weight between the i-th transmittingantenna and j-th transmission information and W represents the weight asthe matrix. The matrix W is called a weight matrix or a precodingmatrix.

The transmission signal x described above may be divided intotransmission signals in a case using the spatial diversity and a caseusing the spatial multiplexing.

In the case using the spatial multiplexing, since different signals aremultiplexed and sent, all elements of an information vector s havedifferent values, while when the spatial diversity is used, since thesame signal is sent through multiple channel paths, all of the elementsof the information vector s have the same value.

A method mixing the spatial multiplexing and the spatial diversity mayalso be considered. That is, for example, a case may also be consideredin which the same signal is transmitted using the spatial diversitythrough three transmitting antennas and different signals are sent byspatial multiplexing through residual transmitting antennas.

Next, when NR receiving antennas are provided, received signals y1, y2,. . . , yNR of the respective antennas are expressed as a vector y asdescribed below.

y=[y ₁ ,y ₂ ,Λ,y _(N) _(R) ]^(T)  [Equation 6]

If channels are modeled in the MIMO antenna communication system, thechannels may be distinguished based on transmitting and receivingantenna indexes and a channel passing through a receiving antenna i froma transmitting antenna j will be represented as hij. Herein, it is notedthat in the case of the order of the index of hij, the receiving antennaindex is earlier and the transmitting antenna index is later.

The multiple channels are gathered into one to be expressed even asvector and matrix forms. An example of expression of the vector will bedescribed below.

FIG. 6 is a diagram illustrating a channel from multiple transmittingantennas to one receiving antenna.

As illustrated in FIG. 6, a channel which reaches receiving antenna Ifrom a total of NT transmitting antennas may be expressed as below.

h _(i) ^(T)=[h _(i1) ,h _(i2) ,Λ,h _(iN) _(T) ]  [Equation 7]

Further, all of channels passing through NR receiving antennas from NTtransmitting antennas may be shown as below through matrix expressionshown in Equation given above.

$\begin{matrix}{H = {\begin{bmatrix}h_{1}^{T} \\h_{2}^{T} \\M \\h_{i}^{T} \\M \\h_{N_{R}}^{T}\end{bmatrix} = \begin{bmatrix}h_{11} & h_{12} & \Lambda & h_{1N_{T}} \\h_{21} & h_{22} & \Lambda & h_{2N_{T}} \\M & \; & O & \; \\h_{i\; 1} & h_{i\; 2} & \Lambda & h_{{iN}_{T}} \\M & \; & O & \; \\h_{N_{R}1} & h_{N_{R}2} & \Lambda & h_{N_{R}N_{T}}\end{bmatrix}}} & \left\lbrack {{Equation}\mspace{14mu} 8} \right\rbrack\end{matrix}$

Since additive white Gaussian noise (AWGN) is added after passingthrough a channel matrix H given above in an actual channel, whitenoises n1, n2, . . . , nNR added to NR receiving antennas, respectivelyare expressed as below.

n=[n ₁ ,n ₂ ,Λ,n _(N) _(R) ]^(T)  [Equation 9]

Each of the transmission signal, the reception signal, the channel, andthe white noise in the MIMO antenna communication system may beexpressed through a relationship given below by modeling thetransmission signal, the reception signal, the channel, and the whitenoise.

$\begin{matrix}{y = {\begin{bmatrix}y_{1} \\y_{2} \\M \\y_{i} \\M \\y_{N_{R}}\end{bmatrix} = {\quad{{\begin{bmatrix}h_{11} & h_{12} & \Lambda & h_{1N_{T}} \\h_{21} & h_{22} & \Lambda & h_{2N_{T}} \\M & \; & O & \; \\h_{i\; 1} & h_{i\; 2} & \Lambda & h_{{iN}_{T}} \\M & \; & O & \; \\h_{N_{R}1} & h_{N_{R}2} & \Lambda & h_{N_{R}N_{T}}\end{bmatrix}\begin{bmatrix}x_{1} \\x_{2} \\M \\x_{j} \\M \\x_{N_{T}}\end{bmatrix}} + {\begin{bmatrix}n_{1} \\n_{2} \\M \\n_{i} \\M \\n_{N_{R}}\end{bmatrix}{Hx}} + n}}}} & \left\lbrack {{Equation}\mspace{14mu} 10} \right\rbrack\end{matrix}$

The number of rows and columns of the channel matrix H representing thestate of the channel is determined by the number of transmitting andreceiving antennas. In the case of the channel matrix H, the number ofrows becomes equivalent to NR which is the number of receiving antennasand the number of columns becomes equivalent to NR which is the numberof transmitting antennas. That is, the channel matrix H becomes an NR×NRmatrix.

In general, a rank of the matrix is defined as the minimum number amongthe numbers of independent rows or columns. Therefore, the rank of thematrix may not be larger than the number of rows or columns. As anequation type example, the rank (rank(H)) of the channel matrix H islimited as below.

rank(H)≤min(N _(T) ,N _(R))  [Equation 11]

Further, when the matrix is subjected to Eigen value decomposition, therank may be defined as not 0 but the number of Eigen values among theEigen values. By a similar method, when the rank is subjected tosingular value decomposition, the rank may be defined as not 0 but thenumber of singular values. Accordingly, a physical meaning of the rankin the channel matrix may be the maximum number which may send differentinformation in a given channel.

In this specification, a ‘rank’ for MIMO transmission represents thenumber of paths to independently transmit the signal at a specific timeand in a specific frequency resource and ‘the number of layers’represents the number of signal streams transmitted through each path.In general, since the transmitter side transmits layers of the numbercorresponding to the number of ranks used for transmitting the signal,the rank has the same meaning as the number layers if not particularlymentioned.

Carrier Aggregation

A communication environment considered in embodiments of the presentinvention includes multi-carrier supporting environments. That is, amulti-carrier system or a carrier aggregation system used in the presentinvention means a system that aggregates and uses one or more componentcarriers (CCs) having a smaller bandwidth smaller than a target band atthe time of configuring a target wideband in order to support awideband.

In the present invention, a multi-carrier means an aggregation ofcarriers (alternatively carrier aggregation). In this case, theaggregation of carriers means both an aggregation between continuouscarriers and an aggregation between non-contiguous carriers. Further,the number of component carriers aggregated between downlink and uplinkmay be differently set. A case where the number of downlink componentcarriers (hereinafter referred to as a “DL CC”) and the number of uplinkcomponent carriers (hereinafter, referred to as an “UL CC”) are the sameis referred to as a “symmetric aggregation”, and a case where the numberof downlink component carriers and the number of uplink componentcarriers are different is referred to as an “asymmetric aggregation.”The carrier aggregation may be used interchangeably with a term, such asa bandwidth aggregation or a spectrum aggregation.

A carrier aggregation configured by combining two or more componentcarriers aims at supporting up to a bandwidth of 100 MHz in the LTE-Asystem. When one or more carriers having the bandwidth than the targetband are combined, the bandwidth of the carriers to be combined may belimited to a bandwidth used in the existing system in order to maintainbackward compatibility with the existing IMT system. For example, theexisting 3GPP LTE system supports bandwidths of 1.4, 3, 5, 10, 15, and20 MHz and a 3GPP LTE-advanced system (that is, LTE-A) may be configuredto support a bandwidth larger than 20 MHz by using on the bandwidth forcompatibility with the existing system. Further, the carrier aggregationsystem used in the preset invention may be configured to support thecarrier aggregation by defining a new bandwidth regardless of thebandwidth used in the existing system.

The LTE-A system uses a concept of the cell in order to manage a radioresource.

The carrier aggregation environment may be called a multi-cellenvironment. The cell is defined as a combination of a pair of adownlink resource (DL CC) and an uplink resource (UL CC), but the uplinkresource is not required. Therefore, the cell may be constituted by onlythe downlink resource or both the downlink resource and the uplinkresource. When a specific terminal has only one configured serving cell,the cell may have one DL CC and one UL CC, but when the specificterminal has two or more configured serving cells, the cell has DL CCsas many as the cells and the number of UL CCs may be equal to or smallerthan the number of DL CCs.

Alternatively, contrary to this, the DL CC and the UL CC may beconfigured. That is, when the specific terminal has multiple configuredserving cells, a carrier aggregation environment having UL CCs more thanDL CCs may also be supported. That is, the carrier aggregation may beappreciated as aggregation of two or more cells having different carrierfrequencies (center frequencies). Herein, the described ‘cell’ needs tobe distinguished from a cell as an area covered by the base stationwhich is generally used.

The cell used in the LTE-A system includes a primary cell (PCell) and asecondary cell (SCell. The P cell and the S cell may be used as theserving cell. In a terminal which is in an RRC_CONNECTED state, but doesnot have the configured carrier aggregation or does not support thecarrier aggregation, only one serving constituted by only the P cell ispresent. On the contrary, in a terminal which is in the RRC_CONNECTEDstate and has the configured carrier aggregation, one or more servingcells may be present and the P cell and one or more S cells are includedin all serving cells.

The serving cell (P cell or S cell) may be configured through an RRCparameter. PhysCellId as a physical layer identifier of the cell hasinteger values of 0 to 503. SCellIndex as a short identifier used toidentify the S cell has integer values of 1 to 7. ServCellIndex as ashort identifier used to identify the serving cell (P cell or S cell)has the integer values of 0 to 7. The value of 0 is applied to the Pcell and SCellIndex is previously granted for application to the S cell.That is, a cell having a smallest cell ID (alternatively, cell index) inServCellIndex becomes the P cell.

The P cell means a cell that operates on a primary frequency(alternatively a primary CC). The terminal may be used to perform aninitial connection establishment process or a connectionre-establishment process and may be designated as a cell indicatedduring a handover process. Further, the P cell means a cell whichbecomes the center of control associated communication among servingcells configured in the carrier aggregation environment. That is, theterminal may be allocated with and transmit the PUCCH only in the P cellthereof and use only the P cell to acquire the system information orchange a monitoring procedure. An evolved universal terrestrial radioaccess (E-UTRAN) may change only the P cell for the handover procedureto the terminal supporting the carrier aggregation environment by usingan RRC connection reconfiguration message (RRCConnectionReconfigutaion)message of an upper layer including mobile control information(mobilityControlInfo).

The S cell means a cell that operates on a secondary frequency(alternatively, secondary CC). Only one P cell may be allocated to aspecific terminal and one or more S cells may be allocated to thespecific terminal. The S cell may be configured after RRC connectionestablishment is achieved and used for providing an additional radioresource. The PUCCH is not present in residual cells other than the Pcell, that is, the S cells among the serving cells configured in thecarrier aggregation environment. The E-UTRAN may provide all systeminformation associated with a related cell which is in an RRC_CONNECTEDstate through a dedicated signal at the time of adding the S cells tothe terminal that supports the carrier aggregation environment. A changeof the system information may be controlled by releasing and adding therelated S cell and in this case, the RRC connection reconfiguration(RRCConnectionReconfigutaion) message of the upper layer may be used.The E-UTRAN may perform having different parameters for each terminalrather than broadcasting in the related S cell.

After an initial security activation process starts, the E-UTRAN addsthe S cells to the P cell initially configured during the connectionestablishment process to configure a network including one or more Scells. In the carrier aggregation environment, the P cell and the S cellmay operate as the respective component carriers. In an embodimentdescribed below, the primary component carrier (PCC) may be used as thesame meaning as the P cell and the secondary component carrier (SCC) maybe used as the same meaning as the S cell.

FIG. 7 illustrates examples of a component carrier and carrieraggregation in the wireless communication system to which the presentinvention may be applied.

FIG. 7a illustrates a single carrier structure used in an LTE system.The component carrier includes the DL CC and the UL CC. One componentcarrier may have a frequency range of 20 MHz.

FIG. 7b illustrates a carrier aggregation structure used in the LTEsystem. In the case of FIG. 7b , a case is illustrated, in which threecomponent carriers having a frequency magnitude of 20 MHz are combined.Each of three DL CCs and three UL CCs is provided, but the number of DLCCs and the number of UL CCs are not limited. In the case of carrieraggregation, the terminal may simultaneously monitor three CCs, andreceive downlink signal/data and transmit uplink signal/data.

When N DL CCs are managed in a specific cell, the network may allocate M(N≤M) DL CCs to the terminal. In this case, the terminal may monitoronly M limited DL CCs and receive the DL signal. Further, the networkgives L (L≤M≤N) DL CCs to allocate a primary DL CC to the terminal andin this case, UE needs to particularly monitor L DL CCs. Such a schememay be similarly applied even to uplink transmission.

A linkage between a carrier frequency (alternatively, DL CC) of thedownlink resource and a carrier frequency (alternatively, UL CC) of theuplink resource may be indicated by an upper-layer message such as theRRC message or the system information. For example, a combination of theDL resource and the UL resource may be configured by a linkage definedby system information block type 2 (SIB2). In detail, the linkage maymean a mapping relationship between the DL CC in which the PDCCHtransporting a UL grant and a UL CC using the UL grant and mean amapping relationship between the DL CC (alternatively, UL CC) in whichdata for the HARQ is transmitted and the UL CC (alternatively, DL CC) inwhich the HARQ ACK/NACK signal is transmitted.

If one or more S cells are configured in a UE, a network may activate ordeactivate the configured S cell(s). A P cell is always activated. Thenetwork activates or deactivates the S cell(s) by sending anactivation/deactivation MAC control element.

The activation/deactivation MAC control element has a fixed size andincludes a single octet including seven C fields and one R field. The Cfield is configured for each S cell index “SCellIndex”, and indicatesthe activation/deactivation state of the S cell. When the value of the Cfield is set to “1”, it indicates that an S cell having a correspondingS cell index is activated. When the value of the C field is set to “0”,it indicates that an S cell having a corresponding S cell index isdeactivated.

Furthermore, the UE maintains a timer “sCellDeactivationTimer” for eachconfigured S cell and deactivates a related S cell when the timerexpires. The same initial value of the timer is applied to each instanceof the timer “sCellDeactivationTimer” and set by RRC signaling. When theS cell(s) are added or after handover, initial S cell(s) are adeactivation state.

The UE performs the following operation on each of the configured Scell(s) in each TTI.

-   -   When the UE receives an activation/deactivation MAC control        element that activates an S cell in a specific TTI (subframe n),        the UE activates the S cell in a corresponding TTI (a subframe        n+8 or thereafter) on predetermined timing and (re)starts a        timer related to the corresponding S cell. What the UE activates        the S cell means that the UE applies a common S cell operation,        such as the transmission of a sounding reference signal (SRS),        the reporting of a channel quality indicator (CQI)/precoding        matrix indicator (PMI)/rank indication (RI)/precoding type        indicator (PTI), the monitoring of a PDCCH and the monitoring of        a PDCCH for an S cell on the S cell.    -   When the UE receives an activation/deactivation MAC control        element that deactivates an S cell in a specific TTI        (subframe n) or a timer related to a specific TTI (subframe        n)-activated S cell expires, the UE deactivates the S cell in a        corresponding TTI (subframe n+8 or thereafter) on predetermined        timing, stops the timer of the corresponding S cell, and flushes        all of HARQ buffers related to the corresponding S cell.    -   If a PDCCH on an activated S cell indicates an uplink grant or        downlink assignment or a PDCCH on a serving cell that schedules        the activated S cell indicates an uplink grant or downlink        assignment for the activated S cell, the UE restarts a timer        related to the corresponding S cell.    -   When the S cell is deactivated, the UE does not send an SRS on        the S cell, does not report a CQI/PMI/RI/PTI for the S cell,        does not send an UL-SCH on the S cell, and does not monitor a        PDCCH on the S cell.

Random Access Procedure

A random access procedure provided by LTE/LTE-A systems is describedbelow.

The random access procedure is used for a UE to obtain uplinksynchronization with an eNB or to have uplink radio resources allocatedthereto. When the UE is powered on, the UE obtains downlinksynchronization with an initial cell and receives system information.The UE obtains information about a set of available random accesspreambles and radio resources used to send a random access preamble fromthe system information. The radio resources used to send the randomaccess preamble may be specified as a combination of at least onesubframe index and an index in a frequency domain. The UE sends a randomaccess preamble randomly selected from the set of random accesspreambles. An eNB that has received the random access preamble sends atiming alignment (TA) value for uplink synchronization to the UE througha random access response. Accordingly, the UE obtains uplinksynchronization.

The random access procedure is common to frequency division duplex (FDD)and time division duplex (TDD). The random access procedure is notrelated to a cell size and is also not related to the number of servingcells if a component aggregation (CA) has been configured.

First, the UE may perform the random access procedure as in thefollowing cases.

-   -   If the UE performs initial access in the RRC idle state because        it does not have RRC connection with the Enb    -   If the UE performs an RRC connection re-establishment procedure    -   If the UE first accesses a target cell in a handover process    -   If the random access procedure is requested by a command from        the eNB    -   If there is data to be transmitted in downlink in an uplink        non-synchronized situation during the RRC connection state    -   If there is a data to be transmitted in uplink in an uplink        non-synchronized situation or in a situation in which designated        radio resources used to request radio resources have not been        allocated during the RRC connection state    -   If the positioning of the UE is performed in a situation in        which timing advance is necessary during the RRC connection        state    -   If a recovery process is performed when a radio link failure or        handover failure occurs

In 3GPP Rel-10, a method for applying a timing advance (TA) valueapplicable to one specific cell (e.g., a P cell) to a plurality of cellsin common in a radio access system supporting a component aggregationhas been taken into consideration. A UE may aggregate a plurality ofcells belonging to different frequency bands (i.e., greatly spaced aparton the frequency) or a plurality of cells having different propagationproperties. Furthermore, in the case of a specific cell, in order toexpand coverage or remove a coverage hole, if the UE performscommunication with an eNB (i.e., a macro eNB) through one cell andperforms communication with a secondary eNB (SeNB) through the othercell in a situation in which a remote radio header (RRH) (i.e.,repeater), a small cell such as a femto cell or a pico cell, or the SeNBhas been disposed within the cell, a plurality of cells may havedifferent delay properties. In this case, if the UE performs uplinktransmission using a method for applying one TA value to a plurality ofcells in common, the synchronization of an uplink signal transmitted onthe plurality of cells may be severely influenced. Accordingly, aplurality of TAs may be used in a CA situation in which a plurality ofcells has been aggregated. In 3GPP Rel-11, in order to support multipleTAs, the independent allocation of the TAs may be taken intoconsideration for each specific cell group. This is called a TA group(TAG). The TAG may include one or more cells. The same TA may be appliedto one or more cells included in a TAG in common. In order to supportsuch multiple TAs, an MAC TA command control element includes a TAGidentity (ID) of 2 bits and a TA command field of 6 bits.

A UE in which a CA has been configured performs a random accessprocedure if it performs the random access procedure in relation to a Pcell. In the case of a TAG to which the P cell belongs (i.e., a primaryTAG (pTAG)), as in a conventional technology, TA determined based on theP cell or coordinated through a random access procedure involved in theP cell may be applied to all of cell(s) within the pTAG. In contrast, inthe case of a TAG including only an S cell (i.e., a secondary TAG(sTAG)), TA determined based on a specific S cell within the sTAG may beapplied to all of cell(s) within the corresponding sTAG. In this case,the TA may be obtained by a random access procedure initiated by an eNB.More specifically, the S cell is configured as a random access channel(RACH) resource within the sTAG. In order to determine the TA, the eNBrequests RACH access in the S cell. That is, the eNB initiates RACHtransmission on S cells in response to a PDCCH order transmitted in theP cell. A response message for an S cell preamble is transmitted througha P cell using an RA-RNTI. The UE may apply TA, determined based on an Scell to which random access has been successfully completed, to all ofcell(s) within a corresponding sTAG. As described above, the randomaccess procedure may be performed even in an S cell in order to obtainthe TA of an sTAG to which the S cell belongs even in the correspondingS cell.

An LTE/LTE-A system provides a contention-based random access procedurefor randomly selecting, by a UE, one preamble within a specific set andusing the selected preamble and a non-contention-based random accessprocedure for using a random access preamble allocated to only aspecific UE by an eNB in a process of selecting a random access preamble(RACH preamble). In this case, the non-contention-based random accessprocedure may be used for only UE positioning and/or timing advancealignment for an sTAG if it is requested in the handover process or inresponse to a command from the eNB. After the random access procedure iscompleted, common uplink/downlink transmission is performed.

A relay node (RN) also supports both the contention-based random accessprocedure and the non-contention-based random access procedure. When arelay node performs the random access procedure, it suspends an RNsubframe configuration at that point of time. That is, this means thatit temporarily discards an RN subframe. Thereafter, an RN subframeconfiguration is restarted at a point of time at which a random accessprocedure is successfully completed.

FIG. 8 is a diagram for illustrating a contention-based random accessprocedure in a wireless communication system to which an embodiment ofthe present invention may be applied.

(1) First Message (Msg 1 or Message 1)

First, UE randomly selects one random access preamble (RACH preamble)from a set of random access preambles indicated by system information ora handover command, selects a physical RACH (PRACH) resource capable ofsending the random access preamble, and sends the selected physical RACH(PRACH).

The random access preamble is transmitted through 6 bits in an RACHtransport channel. The 6 bits include a random identity of 5 bits foridentifying the UE that has performed RACH transmission and 1 bit (e.g.,indicate the size of a third message Msg3) for indicating additionalinformation.

An eNB that has received the random access preamble from the UE decodesthe random access preamble and obtains an RA-RNTI. The RA-RNTI relatedto the PRACH in which the random access preamble has been transmitted isdetermined by the time-frequency resource of the random access preambletransmitted by the corresponding UE.

(2) Second Message (Msg 2 or Message 2)

The eNB sends a random access response, addressed by the RA-RNTIobtained through the preamble on the first message, to the UE. Therandom access response may include a random access (RA) preambleindex/identifier, uplink (UL) assignment providing notification ofuplink radio resources, a temporary C-RNTI, and a time alignment command(TAC). The TAC is information indicative of a time alignment commandthat is transmitted from the eNB to the UE in order to maintain uplinktime alignment. The UE updates uplink transmission timing using the TAC.When the UE updates time synchronization, it initiates or restarts atime alignment timer. An UL grant includes uplink resource allocationused for the transmission of a scheduling message (third message) to bedescribed later and a transmit power command (TPC). The TPC is used todetermine transmission power for a scheduled PUSCH.

After the UE sends the random access preamble, it attempts to receiveits own random access response within a random access response windowindicated by the eNB through system information or a handover command,detects a PDCCH masked with an RA-RNTI corresponding to the PRACH, andreceives a PDSCH indicated by the detected PDCCH. Information about therandom access response may be transmitted in the form of a MAC packetdata unit (PDU). The MAC PDU may be transferred through the PDSCH. ThePDCCH may include information about the UE that needs to receive thePDSCH, information about the frequency and time of the radio resourcesof the PDSCH, and the transmission format of the PDSCH. As describedabove, once the UE successfully detects the PDCCH transmitted thereto,it may properly receive the random access response transmitted throughthe PDSCH based on the pieces of information of the PDCCH.

The random access response window means a maximum time interval duringwhich the UE that has sent the preamble waits to receive the randomaccess response message. The random access response window has a lengthof “ra-ResponseWindowSize” that starts from a subframe subsequent tothree subframes from the last subframe in which the preamble istransmitted. That is, the UE waits to receive the random access responseduring a random access window secured after three subframes from asubframe in which the preamble has been transmitted. The UE may obtainthe parameter value of a random access window size“ra-ResponseWindowsize” through the system information. The randomaccess window size may be determined to be a value between 2 and 10.

When the UE successfully receives the random access response having thesame random access preamble index/identifier as the random accesspreamble transmitted to the eNB, it suspends the monitoring of therandom access response. In contrast, if the UE has not received a randomaccess response message until the random access response window isterminated or the UE does not receive a valid random access responsehaving the same random access preamble index as the random accesspreamble transmitted to the eNB, the UE considers the reception of arandom access response to be a failure and then may perform preambleretransmission.

As described above, the reason why the random access preamble index isnecessary for the random access response is to provide notification thatan UL grant, a TC-RNTI and a TAC are valid for which UE because randomaccess response information for one or more UEs may be included in onerandom access response.

(3) Third Message (Msg 3 or Message 3)

When the UE receives a valid random access response, it processes eachof pieces of information included in the random access response. Thatis, the UE applies a TAC to each of the pieces of information and storesa TC-RNTI. Furthermore, the UE sends data, stored in the buffer of theUE, or newly generated data to the eNB using an UL grant. If the UEperforms first connection, an RRC connection request generated in theRRC layer and transferred through a CCCH may be included in the thirdmessage and transmitted. In the case of an RRC connectionre-establishment procedure, an RRC connection re-establishment requestgenerated in the RRC layer and transferred through a CCCH may beincluded in the third message and transmitted. Furthermore, the thirdmessage may include an NAS access request message.

The third message may include the identity of the UE. In thecontention-based random access procedure, the eNB is unable to determinewhich UE can perform the random access procedure. The reason for this isthat the UE has to be identified in order to perform a collisionresolution.

A method for including the identity of UE includes two methods. In thefirst method, if UE has already had a valid cell identity (C-RNTI)allocated in a corresponding cell prior to a random access procedure,the UE sends its own cell identity through an uplink transmission signalcorresponding to an UL grant. In contrast, if a valid cell identity hasnot been allocated to the UE prior to a random access procedure, the UEincludes its own unique identity (e.g., an S-TMSI or a random number) inan uplink transmission signal and sends the uplink transmission signal.In general, the unique identity is longer than a C-RNTI. In transmissionon an UL-SCH, UE-specific scrambling is used. In this case, if a C-RNTIhas not been allocated to the UE, the scrambling may not be based on theC-RNTI, and instead a TC-RNTI received in a random access response isused. If the UE has sent data corresponding to the UL grant, itinitiates a timer for a collision resolution (i.e., a contentionresolution timer).

(4) Fourth Message (Msg 4 or Message 4)

When the C-RNTI of the UE is received through the third message from theUE, the eNB sends a fourth message to the UE using the received C-RNTI.In contrast, when the eNB receives a unique identity (i.e., an S-TMSI ora random number) through the third message from the UE, it sends thefourth message to the UE using a TC-RNTI allocated to the correspondingUE in a random access response. In this case, the fourth message maycorrespond to an RRC connection setup message including a C-RNTI.

After the UE sends data including its own identity through the UL grantincluded in the random access response, it waits for an instruction fromthe eNB for a collision resolution. That is, the UE attempts to receivea PDCCH in order to receive a specific message. A method for receivingthe PDCCH includes two methods. As described above, if the third messagetransmitted in response to the UL grant includes a C-RNTI as its ownidentity, the UE attempts the reception of a PDCCH using its own C-RNTI.If the identity is a unique identity (i.e., an S-TMSI or a randomnumber), the UE attempts the reception of a PDCCH using a TC-RNTIincluded in the random access response. Thereafter, in the former case,if the UE has received a PDCCH through its own C-RNTI before a collisionresolution timer expires, the UE determines that the random accessprocedure has been normally performed and terminates the random accessprocedure. In the latter case, if the UE has received a PDCCH through aTC-RNTI before a collision resolution timer expires, the UE checks datain which a PDSCH indicated by the PDCCH is transferred. If, as a resultof the check, it is found that the unique identity of the UE has beenincluded in the contents of the data, the UE determines that the randomaccess procedure has been normally performed and terminates the randomaccess procedure. The UE obtains the C-RNTI through the fourth message.Thereafter, the UE and a network send or receive a UE-dedicated messageusing the C-RNTI.

A method for a collision resolution in random access is described below.

The reason why a collision occurs in performing random access is thatthe number of random access preambles is basically limited. That is, aUE randomly selects one of common random access preambles and sends theselected random access preamble because an eNB cannot assign a randomaccess preamble unique to a UE to all of UEs. Accordingly, two or moreUEs may select the same random access preamble and send it through thesame radio resources (PRACH resource), but the eNB determines thereceived random access preambles to be one random access preambletransmitted by one UE. For this reason, the eNB sends a random accessresponse to the UE, and expects that the random access response will bereceived by one UE. As described above, however, since a collision mayoccur, two or more UEs receive one random access response and thus theeNB performs an operation according to the reception of each randomaccess response for each UE. That is, there is a problem in that the twoor more UEs send different data through the same radio resources usingone UL grant included in the random access response. Accordingly, thetransmission of the data may all fail, and the eNB may receive only thedata of a specific UE depending on the location or transmission power ofthe UEs. In the latter case, all of the two or more UEs assume that thetransmission of their data was successful, and thus the eNB has tonotify UEs that have failed in the contention of information about thefailure. That is, providing notification of information about thefailure or success of the contention is called a collision resolution.

A collision resolution method includes two methods. One method is amethod using a collision resolution timer, and the other method is amethod of sending the identity of a UE that was successful in acontention to other UEs. The former method is used when a UE already hasa unique C-RNTI prior to a random access process. That is, the UE thathas already had the C-RNTI sends data, including its own C-RNTI, to aneNB in response to a random access response, and drives a collisionresolution timer. Furthermore, when PDCCH information indicated by itsown C-RNTI is received before the collision resolution timer expires,the UE determines that it was successful in the contention and normallyterminates the random access. In contrast, if the UE does not receive aPDCCH indicated by its own C-RNTI before the collision resolution timerexpires, the UE determines that it failed in the contention and mayperform a random access process again or may notify a higher layer ofthe failure of the contention. In the latter method of the twocontention resolution methods, that is, the method of sending theidentity of a successful UE, is used if a UE does not have a unique cellidentity prior to a random access process. That is, if the UE does nothave its own cell identity, the UE includes an identity (or an S-TMSI ora random number) higher than the cell identity in data based on UL grantinformation included in a random access response, sends the data, anddrives a collision resolution timer. If data including its own higheridentity is transmitted through a DL-SCH before the collision resolutiontimer expires, the UE determines that the random access process wassuccessful. In contrast, if data including its own higher identity isnot received through a DL-SCH before the collision resolution timerexpires, the UE determines that the random access process has failed.

Unlike in the contention-based random access procedure shown in FIG. 8,the operation in the non-contention-based random access procedure isterminated by only the transmission of the first message and the secondmessage. In this case, before a UE sends a random access preamble to aneNB as the first message, the eNB allocates the random access preambleto the UE, and the UE sends the allocated random access preamble to theeNB as the first message and receives a random access response from theeNB. Accordingly, the random connection procedure is terminated.

Reference Signal (RS)

In the wireless communication system, since the data is transmittedthrough the radio channel, the signal may be distorted duringtransmission. In order for the receiver side to accurately receive thedistorted signal, the distortion of the received signal needs to becorrected by using channel information. In order to detect the channelinformation, a signal transmitting method know by both the transmitterside and the receiver side and a method for detecting the channelinformation by using a distortion degree when the signal is transmittedthrough the channel are primarily used. The aforementioned signal isreferred to as a pilot signal or a reference signal (RS).

Recently, when packets are transmitted in most of mobile communicationsystems, multiple transmitting antennas and multiple receiving antennasare adopted to increase transceiving efficiency rather than a singletransmitting antenna and a single receiving antenna. When the data istransmitted and received by using the MIMO antenna, a channel statebetween the transmitting antenna and the receiving antenna need to bedetected in order to accurately receive the signal. Therefore, therespective transmitting antennas need to have individual referencesignals.

Reference signal in a wireless communication system may be mainlycategorized into two types. In particular, there are a reference signalfor the purpose of channel information acquisition and a referencesignal used for data demodulation. Since the object of the formerreference signal is to enable a UE (user equipment) to acquire a channelinformation in DL (downlink), the former reference signal should betransmitted on broadband. And, even if the UE does not receive DL datain a specific subframe, it should perform a channel measurement byreceiving the corresponding reference signal. Moreover, thecorresponding reference signal may be used for a measurement formobility management of a handover or the like. The latter referencesignal is the reference signal transmitted together when a base stationtransmits DL data. If a UE receives the corresponding reference signal,the UE can perform channel estimation, thereby demodulating data. And,the corresponding reference signal should be transmitted in a datatransmitted region.

The DL reference signals are categorized into a common reference signal(CRS) shared by all terminals for an acquisition of information on achannel state and a measurement associated with a handover or the likeand a dedicated reference signal (DRS) used for a data demodulation fora specific terminal. Information for demodulation and channelmeasurement may be provided by using the reference signals. That is, theDRS is used only for data demodulation only, while the CRS is used fortwo kinds of purposes including channel information acquisition and datademodulation.

The receiver side (that is, terminal) measures the channel state fromthe CRS and feeds back the indicators associated with the channelquality, such as the channel quality indicator (CQI), the precodingmatrix index (PMI), and/or the rank indicator (RI) to the transmittingside (that is, base station). The CRS is also referred to as acell-specific RS. On the contrary, a reference signal associated with afeed-back of channel state information (CSI) may be defined as CSI-RS.

The DRS may be transmitted through resource elements when datademodulation on the PDSCH is required. The terminal may receive whetherthe DRS is present through the upper layer and is valid only when thecorresponding PDSCH is mapped. The DRS may be referred to as theUE-specific RS or the demodulation RS (DMRS).

FIG. 9 illustrates a reference signal pattern mapped to a downlinkresource block pair in the wireless communication system to which thepresent invention may be applied.

Referring to FIG. 9, as a unit in which the reference signal is mapped,the downlink resource block pair may be expressed by one subframe in thetimedomain×12 subcarriers in the frequency domain. That is, one resourceblock pair has a length of 14 OFDM symbols in the case of a normalcyclic prefix (CP) (FIG. 9a ) and a length of 12 OFDM symbols in thecase of an extended cyclic prefix (CP) (FIG. 9b ). Resource elements(REs) represented as ‘0’, ‘1’, ‘2’, and ‘3’ in a resource block latticemean the positions of the CRSs of antenna port indexes ‘0’, ‘1’, ‘2’,and ‘3’, respectively and resource elements represented as ‘D’ means theposition of the DRS.

Hereinafter, when the CRS is described in more detail, the CRS is usedto estimate a channel of a physical antenna and distributed in a wholefrequency band as the reference signal which may be commonly received byall terminals positioned in the cell. That is, the CRS is transmitted ineach subframe across a broadband as a cell-specific signal. Further, theCRS may be used for the channel quality information (CSI) and datademodulation.

The CRS is defined as various formats according to an antenna array atthe transmitter side (base station). The RSs are transmitted based onmaximum 4 antenna ports depending on the number of transmitting antennasof a base station in the 3GPP LTE system (for example, release-8). Thetransmitter side has three types of antenna arrays of three singletransmitting antennas, two transmitting antennas, and four transmittingantennas. For instance, in case that the number of the transmittingantennas of the base station is 2, CRSs for antenna #1 and antenna #2are transmitted. For another instance, in case that the number of thetransmitting antennas of the base station is 4, CRSs for antennas #1 to#4 are transmitted.

When the base station uses the single transmitting antenna, a referencesignal for a single antenna port is arrayed.

When the base station uses two transmitting antennas, reference signalsfor two transmitting antenna ports are arrayed by using a time divisionmultiplexing (TDM) scheme and/or a frequency division multiplexing (FDM)scheme. That is, different time resources and/or different frequencyresources are allocated to the reference signals for two antenna portswhich are distinguished from each other.

Moreover, when the base station uses four transmitting antennas,reference signals for four transmitting antenna ports are arrayed byusing the TDM and/or FDM scheme. Channel information measured by adownlink signal receiving side (terminal) may be used to demodulate datatransmitted by using a transmission scheme such as single transmittingantenna transmission, transmission diversity, closed-loop spatialmultiplexing, open-loop spatial multiplexing, or multi-user MIMO.

In the case where the MIMO antenna is supported, when the referencesignal is transmitted from a specific antenna port, the reference signalis transmitted to the positions of specific resource elements accordingto a pattern of the reference signal and not transmitted to thepositions of the specific resource elements for another antenna port.That is, reference signals among different antennas are not duplicatedwith each other.

The DRS is described in more detail below. The DRS is used to demodulatedata. Precoding weight used for a specific UE in MIMO antennatransmission is used without any change in order for a UE to estimate acorresponding channel in association with a transport channeltransmitted in each transmission antenna when the UE receives areference signal.

The 3GPP LTE system (e.g., Release-8) supports up to a maximum of fourtransmission antennas, and a DRA for rank 1 beamforming is defined. TheDRS for rank 1 beamforming further indicates a reference signal anantenna port index 5.

The LTE-A system which is an evolved version of the LTE system shouldsupport maximum eight transmitting antennas for downlink transmission.Accordingly, reference signals for maximum eight transmitting antennasshould also be supported. In the LTE system, since the downlinkreference signals are defined for maximum four antenna ports, if thebase station includes four or more downlink transmitting antennas andmaximum eight downlink transmitting antennas in the LTE-A system, thereference signals for these antenna ports should be definedadditionally. The reference signals for maximum eight transmittingantenna ports should be designed for two types of reference signals,i.e., the reference signal for channel measurement and the referencesignal for data demodulation.

One of important considerations in designing the LTE-A system is thebackward compatibility. That is, the backward compatibility means thatthe LTE user equipment should be operated normally even in the LTE-Asystem without any problem and the LTE-A system should also support suchnormal operation. In view of reference signal transmission, thereference signals for maximum eight transmitting antenna ports should bedefined additionally in the time-frequency domain to which CRS definedin the LTE is transmitted on full band of each subframe. However, in theLTE-A system, if reference signal patterns for maximum eighttransmitting antennas are added to full band per subframe in the samemanner as the CRS of the existing LTE system, the RS overhead becomestoo great.

Accordingly, the reference signal designed newly in the LTE-A system maybe divided into two types. Examples of the two types of referencesignals include a channel state information-reference signal (CSI-RS)(or may be referred to as channel state indication-RS) for channelmeasurement for selection of modulation and coding scheme (MCS) and aprecoding matrix index (PMI), and a data demodulation-reference signal(DM-RS) for demodulation of data transmitted to eight transmittingantennas.

The CSI-RS for the channel measurement purpose is designed for channelmeasurement mainly unlike the existing CRS used for channel measurement,handover measurement, and data demodulation. The CSI-RS may also be usedfor handover measurement. Since the CSI-RS is transmitted only to obtainchannel state information, it may not be transmitted per subframe unlikethe CRS of the existing LTE system. Accordingly, in order to reduceoverhead, the CSI-RS may intermittently be transmitted on the time axis.

The DM-RS is dedicatedly transmitted to the UE which is scheduled in thecorresponding time-frequency domain for data demodulation. In otherwords, the DM-RS of a specific UE is only transmitted to the regionwhere the corresponding user equipment is scheduled, i.e., thetime-frequency domain that receives data.

In the LTE-A system, an eNB should transmit the CSI-RSs for all theantenna ports. Since the transmission of CSI-RSs for up to eighttransmission antenna ports in every subframe leads to too much overhead,the CSI-RSs should be transmitted intermittently along the time axis,thereby reducing CSI-RS overhead. Therefore, the CSI-RSs may betransmitted periodically at every integer multiple of one subframe, orin a predetermined transmission pattern. The CSI-RS transmission periodor pattern of the CSI-RSs may be configured by the eNB.

In order to measure the CSI-RSs, a UE should have knowledge of theinformation for each of the CSI-RS antenna ports in the cell to whichthe UE belong such as the transmission subframe index, thetime-frequency position of the CSI-RS resource element (RE) in thetransmission subframe, the CSI-RS sequence, and the like.

In the LTE-A system, an eNB should transmit each of the CSI-RSs formaximum eight antenna ports, respectively. The resources used fortransmitting the CSI-RS of different antenna ports should be orthogonal.When an eNB transmits the CSI-RS for different antenna ports, by mappingthe CSI-RS for each of the antenna ports to different REs, the resourcesmay be orthogonally allocated in the FDM/TDM scheme. Otherwise, theCSI-RSs for different antenna ports may be transmitted in the CDM schemewith being mapped to the mutually orthogonal codes.

When an eNB notifies the information of the CSI-RS to the UE in its owncell, the information of the time-frequency in which the CSI-RS for eachantenna port is mapped should be notified. Particularly, the informationincludes the subframe numbers on which the CSI-RS is transmitted, theperiod of the CSI-RS being transmitted, the subframe offset in which theCSI-RS is transmitted, the OFDM symbol number in which the CSI-RS RE ofa specific antenna is transmitted, the frequency spacing, the offset orshift value of RE on the frequency axis.

The CSI-RS is transmitted through 1, 2, 4 or 8 antenna ports. In thiscase, the antenna port which is used is p=15, p=15, 16 p=15, . . . , 18,or p=15, . . . , 22. The CSI-RS may be defined only for the subcarrierinterval Δf=15 kHz.

(k′,l′) (herein, k′ is a subcarrier index in a resource block, and l′represents an OFDM symbol index in a slot) and the condition of n_(s) isdetermined according to the CSI-RS configuration shown in Table 3 orTable 4 below.

Table 3 exemplifies the mapping of (k′,l′) according to the CSI-RSconfiguration for the normal CP.

CSI reference Number of CSI reference signals configured signal 1 or 2 48 configuration (k′, l′) n_(s) mod 2 (k′, l′) n_(s) mod 2 (k′, l′) n_(s)mod 2 Frame structured type 1 and 2 0 (9, 5) 0 (9, 5) 0 (9, 5) 0 1 (11,2)  1 (11, 2)  1 (11, 2)  1 2 (9, 2) 1 (9, 2) 1 (9, 2) 1 3 (7, 2) 1 (7,2) 1 (7, 2) 1 4 (9, 5) 1 (9, 5) 1 (9, 5) 1 5 (8, 5) 0 (8, 5) 0 6 (10,2)  1 (10, 2)  1 7 (8, 2) 1 (8, 2) 1 8 (6, 2) 1 (6, 2) 1 9 (8, 5) 1 (8,5) 1 10 (3, 5) 0 11 (2, 5) 0 12 (5, 2) 1 13 (4, 2) 1 14 (3, 2) 1 15 (2,2) 1 16 (1, 2) 1 17 (0, 2) 1 18 (3, 5) 1 19 (2, 5) 1 Frame structuretype 2 only 20 (11, 1)  1 (11, 1)  1 (11, 1)  1 21 (9, 1) 1 (9, 1) 1(9, 1) 1 22 (7, 1) 1 (7, 1) 1 (7, 1) 1 23 (10, 1)  1 (10, 1)  1 24(8, 1) 1 (8, 1) 1 25 (6, 1) 1 (6, 1) 1 26 (5, 1) 1 27 (4, 1) 1 28 (3, 1)1 29 (2, 1) 1 30 (1, 1) 1 31 (0, 1) 1

Table 4 illustrates mapping of (k′,l′) from the CSI-RS configuration inthe extended CP.

TABLE 4 CSI reference Number of CSI reference signals configured signal1 or 2 4 8 configuration (k′, l′) n_(s) mod 2 (k′, l′) n_(s) mod 2 (k′,l′) n_(s) mod 2 Frame structure type 1 and 2 0 (11, 4)  0 (11, 4)  0(11, 4)  0 1 (9, 4) 0 (9, 4) 0 (9, 4) 0 2 (10, 4)  1 (10, 4)  1 (10, 4) 1 3 (9, 4) 1 (9, 4) 1 (9, 4) 1 4 (5, 4) 0 (5, 4) 0 5 (3, 4) 0 (3, 4) 0 6(4, 4) 1 (4, 4) 1 7 (3, 4) 1 (3, 4) 1 8 (8, 4) 0 9 (6, 4) 0 10 (2, 4) 011 (0, 4) 0 12 (7, 4) 1 13 (6, 4) 1 14 (1, 4) 1 15 (0, 4) 1 Framestructure type 2 only 16 (11, 1)  1 (11, 1)  1 (11, 1)  1 17 (10, 1)  1(10, 1)  1 (10, 1)  1 18 (9, 1) 1 (9, 1) 1 (9, 1) 1 19 (5, 1) 1 (5, 1) 120 (4, 1) 1 (4, 1) 1 21 (3, 1) 1 (3, 1) 1 22 (8, 1) 1 23 (7, 1) 1 24(6, 1) 1 25 (2, 1) 1 26 (1, 1) 1 27 (0, 1) 1

Referring to Table 3 and Table 4, for the CSI-RS transmission, in orderto decrease the inter-cell interference (ICI) in the multi-cellenvironment including the heterogeneous network (HetNet) environment,different configurations of maximum 32 (in the case of normal CP) ormaximum 28 (in the case of extended CP) are defined.

The CSI-RS configuration is different depending on the number of antennaports in a cell and the CP, neighbor cells may have differentconfigurations to the maximum. In addition, the CSI-RS configuration maybe divided into the case of being applied to both the FDD frame and theTDD frame and the case of being applied to only the TDD frame.

Based on Table 3 and Table 4, (k′,l′) and n_(s) are determined accordingto the CSI-RS configuration. By applying these values to Equation 19,the time-frequency resource that each CSI-RS antenna port uses fortransmitting the CSI-RS is determined.

FIG. 10 is a diagram illustrating the CSI-RS configuration in a wirelesscommunication system to which the present invention may be applied.

FIG. 10(a) shows twenty CSI-RS configurations that are usable in theCSI-RS transmission through one or two CSI-RS antenna ports, and FIG.10(b) shows ten CSI-RS configurations that are usable by four CSI-RSantenna ports. FIG. 10(c) shows five CSI-RS configurations that areusable in the CSI-RS transmission through eight CSI-RS antenna ports.

As such, according to each CSI-RS configuration, the radio resource(i.e., RE pair) in which the CSI-RS is transmitted is determined.

When one or two CSI-RS antenna ports are configured for transmitting theCSI-RS for a specific cell, the CSI-RS is transmitted on the radioresource according to the configured CSI-RS configuration among twentyCSI-RS configurations shown in FIG. 10(a).

Similarly, when four CSI-RS antenna ports are configured fortransmitting the CSI-RS for a specific cell, the CSI-RS is transmittedon the radio resource according to the configured CSI-RS configurationamong ten CSI-RS configurations shown in FIG. 10(b). In addition, wheneight CSI-RS antenna ports are configured for transmitting the CSI-RSfor a specific cell, the CSI-RS is transmitted on the radio resourceaccording to the configured CSI-RS configuration among five CSI-RSconfigurations shown in FIG. 10(c).

The CSI-RS for each of the antenna ports is transmitted with being CDMto the same radio resource for each of two antenna ports (i.e., {15,16},{17,18}, {19,20}, {21,22}). As an example of antenna ports 15 and 16,although the respective CSI-RS complex symbols are the same for antennaports 15 and 16, the CSI-RS complex symbols are mapped to the same radioresource with being multiplied by different orthogonal codes (e.g.,Walsh code). To the complex symbol of the CSI-RS for antenna port 15,[1, 1] is multiplied, and [1, −1] is multiplied to the complex symbol ofthe CSI-RS for antenna port 16, and the complex symbols are mapped tothe same radio resource. This procedure is the same for antenna ports{17,18}, {19,20} and {21,22}.

A UE may detect the CSI-RS for a specific antenna port by multiplying acode multiplied by the transmitted code. That is, in order to detect theCSI-RS for antenna port 15, the multiplied code [1 1] is multiplied, andin order to detect the CSI-RS for antenna port 16, the multiplied code[1 −1] is multiplied.

Referring to FIGS. 10(a) to (c), when a radio resource is correspondingto the same CSI-RS configuration index, the radio resource according tothe CSI-RS configuration including a large number of antenna portsincludes the radio resource according to the CSI-RS configurationincluding a small number of antenna ports. For example, in the case ofCSI-RS configuration 0, the radio resource for eight antenna portsincludes all of the radio resource for four antenna ports and one or twoantenna ports.

A plurality of CSI-RS configurations may be used in a cell. Zero or oneCSI-RS configuration may be used for the non-zero power (NZP) CSI-RS,and zero or several CSI-RS configurations may be used for the zero powerCSI-RS.

A UE presumes the zero power transmission for the REs (except the caseof being overlapped with the RE that presumes the NZP CSI-RS that isconfigured by a high layer) that corresponds to four CSI-RS column inTable 3 and Table 4 above, for every bit that is configured as ‘1’ inthe Zero Power CSI-RS (ZP-CSI-RS) which is the bitmap of 16 bitsconfigured by a high layer. The Most Significant Bit (MSB) correspondsto the lowest CSI-RS configuration index, and the next bit in the bitmapcorresponds to the next CSI-RS configuration index in order.

The CSI-RS is transmitted in the downlink slot only that satisfies thecondition of n_(s) mod 2 in Table 3 and Table 4 above and the CSI-RSsubframe configuration.

In the case of frame structure type 2 (TDD), in the subframe thatcollides with a special subframe, SS, PBCH or SIB 1(SystemInformationBlockType1) message transmission or the subframe thatis configured to transmit a paging message, the CSI-RS is nottransmitted.

In addition, the RE in which the CSI-RS for a certain antenna port thatis belonged to an antenna port set S (S={15}, S={15,16}, S={17,18},S={19,20} or S={21,22}) is transmitted is not used for transmitting thePDSCH or the CSI-RS of another antenna port.

Since the time-frequency resources used for transmitting the CSI-RS isunable to be used for transmitting data, the data throughput decreasesas the CSI-RS overhead increases. Considering this, the CSI-RS is notconfigured to be transmitted in every subframe, but configured to betransmitted in a certain transmission period that corresponds to aplurality of subframes. In this case, the CSI-RS transmission overheadmay be significantly decreased in comparison with the case that theCSI-RS is transmitted in every subframe.

The subframe period (hereinafter, referred to as ‘CSI-RS transmissionperiod’; T_(CSI-RS)) for transmitting the CSI-RS and the subframe offset(Δ_(CSI-RS)) are represented in Table 5 below.

Table 5 exemplifies the configuration of CSI-RS subframe.

TABLE 5 CSI-RS CSI-RS CSI-RS- periodicity subframe offset SubframeConfig(subframes) (subframes) I_(CSI-RS) T_(CSI-RS) Δ_(CSI-RS) 0-4 5I_(CSI-RS)  5-14 10 I_(CSI-RS) − 5 15-34 20 I_(CSI-RS) 15 35-74 40I_(CSI-RS) − 35  75-154 80 I_(CSI-RS) − 75

Referring to Table 5, according to the CSI-RS subframe configuration(I_(CSI-RS)), the CSI-RS transmission period (T_(CSI-RS)) and thesubframe offset (Δ_(CSI-RS)) are determined.

The CSI-RS subframe configuration in Table 5 is configured as one of the‘SubframeConfig’ field and the ‘zeroTxPowerSubframeConfig’ field inTable 2 above. The CSI-RS subframe configuration may be separatelyconfigured for the NZP CSI-RS and the ZP CSI-RS.

The subframe including the CSI-RS satisfies Equation 12 below.

(10n _(f) +└n _(s)/2┘−Δ_(CSI-RS))mod T _(CSI-RS)=0  [Equation 12]

In Equation 12, T_(CSI-RS) represents the CSI-RS transmission period,Δ_(CSI-RS) represents the subframe offset value, n_(f) represents thesystem frame number, and n_(s) represents the slot number.

In the case of a UE in which transmission mode 9 is set for a servingcell, a single CSI-RS resource may be configured in the UE. In the caseof a UE in which transmission mode 10 is set for a serving cell, one ormore CSI-RS resources may be configured in the UE.

For each CSI-RS resource configuration, the following parameters may beset through high layer signaling.

-   -   If transmission mode 10 is set, the CSI-RS resource        configuration identifier    -   The number of CSI-RS ports    -   The CSI-RS configuration (refer to Table 3 and Table 4)    -   The CSI-RS subframe configuration (I_(CSI-RS) refer to Table 5)    -   If transmission mode 9 is set, the transmission power (P_(c))        for the CSI feedback    -   If transmission mode 10 is set, the transmission power (P_(c))        for the CSI feedback with respect to each CSI process. When the        CSI subframe sets C_(CSI,0) and C_(CSI,1) are set by a high        layer for the CSI process, P_(c) is set in each CSI subframe set        of the CSI process.    -   The pseudo-random sequence generator parameter (n_(ID))    -   If transmission mode 10 is set, the QCL scrambling identifier        (qcl-ScramblingIdentity-r11) for assuming the Quasi Co-Located        (QCL) type B UE, the CRS port count (crs-PortsCount-r11), and        the high layer parameter (‘qcl-CRS-Info-r11’) that includes the        MBSFN subframe configuration list (mbsfn-SubframeConfigList-r11)        parameter.

When the CSI feedback value obtained by a UE has the value in the rangeof [−8, 15] dB, P_(c) is presumed by the ratio of the PDSCH EPRE for theCSI-RS EPRE. Herein, the PDSCH EPRE corresponds to the symbol in whichthe ratio of PDSCH EPRE for the CRS EPRE is ρ_(A).

In the same subframe of a serving cell, the CSI-RS and the PMCH are notconfigured together.

When four CRS antenna ports are configured in frame structure type 2,the CSI-RS configuration index belonged to [20-31] set in the case ofthe normal CP (refer to Table 3) or [16-27] set in the case of theextended CP (refer to Table 4) is not configured to a UE.

A UE may assume that the CSI-RS antenna port of the CSI-RS resourceconfiguration has the QCL relation with the delay spread, the Dopplerspread, the Doppler shift, the average gain and the average delay.

The UE to which transmission mode 10 and QCL type B are configured mayassume that the antenna ports 0 to 3 corresponding to the CSI-RSresource configuration and the antenna ports 15 to 22 corresponding tothe CSI-RS resource configuration have the QCL relation with the Dopplerspread and the Doppler shift.

For the UE to which transmission mode 10 is configured, one or moreChannel-State Information-Interference Measurement (CSI-IM) resourceconfiguration may be set.

The following parameters may be configured for each CSI-IM resourceconfiguration through high layer signaling.

-   -   The ZP CSI-RS configuration (refer to Table 3 and Table 4)    -   The ZP CSI-RS subframe configuration refer to Table 5)

The CSI-IM resource configuration is the same as one of the configuredZP CSI-RS resource configuration.

In the same subframe in a serving cell, the CSI-IM resource and the PMCHare not configured simultaneously.

For a UE in which transmission modes 1 to 9 are set, a ZP CSI-RSresource configuration may be configured in the UE for a serving cell.For a UE in which transmission mode 10 is set, one or more ZP CSI-RSresource configurations may be configured in the UE for the servingcell.

The following parameters may be configured for the ZP CSI-RS resourceconfiguration through high layer signaling.

-   -   The ZP CSI-RS configuration list (refer to Table 3 and Table 4)    -   The ZP CSI-RS subframe configuration refer to Table 5)

In the same subframe in a serving cell, the ZP CSI-RS resource and thePMCH are not configured simultaneously.

Cell Measurement/Measurement Report

For one or several methods among the several methods (handover, randomaccess, cell search, etc.) for guaranteeing the mobility of UE, the UEreports the result of a cell measurement to an eNB (or network).

In the 3GPP LTE/LTE-A system, the cell-specific reference signal (CRS)is transmitted through 0, 4, 7 and 11th OFDM symbols in each subframe onthe time axis, and used for the cell measurement basically. That is, aUE performs the cell measurement using the CRS that is received from aserving cell and a neighbor cell, respectively.

The cell measurement is the concept that includes the Radio resourcemanagement (RRM) measurement such as the Reference signal receive power(RSRP) that measures the signal strength of the serving cell and theneighbor cell or the signal strength in comparison with total receptionpower, and so on, the Received signal strength indicator (RSSI), theReference signal received quality (RSRQ), and the like and the RadioLink Monitoring (RLM) measurement that may evaluate the radio linkfailure by measuring the link quality from the serving cell.

The RSRP is a linear average of the power distribution of the RE inwhich the CRS is transmitted in a measurement frequency band. In orderto determine the RSRP, CRS (RO) that corresponds to antenna port ‘0’ maybe used. In addition, in order to determine the RSRP, CRS (R1) thatcorresponds to antenna port ‘1’ may be additionally used. The number ofREs used in the measurement frequency band and the measurement durationby a UE in order to determine the RSRP may be determined by the UEwithin the limit that satisfies the corresponding measurement accuracyrequirements. In addition, the power per RE may be determined by theenergy received in the remaining part of the symbol except the CP.

The RSSI is obtained as the linear average of the total reception powerthat is detected from all sources including the serving cell and thenon-serving cell of the co-channel, the interference from an adjacentchannel, the thermal noise, and so on by the corresponding UE in theOFDM symbols including the RS that corresponds to antenna port ‘0’. Whena specific subframe is indicated by high layer signaling for performingthe RSRQ measurement, the RSSI is measured through all OFDM symbols inthe indicated subframes.

The RSRQ is obtained by N×RSRP/RSSI. Herein, N means the number of RBsof the RSSI measurement bandwidth. In addition, the measurement of thenumerator and the denominator in the above numerical expression may beobtained by the same RB set.

A BS may forward the configuration information for the measurement to aUE through high layer signaling (e.g., RRC Connection Reconfigurationmessage).

The RRC Connection Reconfiguration message includes a radio resourceconfiguration dedicated (‘radioResourceConfigDedicated’) InformationElement (IE) and the measurement configuration (‘measConfig’) IE.

The ‘measConfig’ IE specifies the measurement that should be performedby the UE, and includes the configuration information for theintra-frequency mobility, the inter-frequency mobility, the inter-RATmobility as well as the configuration of the measurement gap.

Particularly, the ‘measConfig’ IE includes ‘measObjectToRemoveList’ thatrepresents the list of the measurement object (‘measObject’) that is tobe removed from the measurement and ‘measObjectToAddModList’ thatrepresents the list that is going to be newly added or amended. Inaddition, ‘MeasObjectCDMA2000’, ‘MeasObjctEUTRA’, ‘MeasObjectGERAN’ andso on are included in the ‘measObject’ according to the communicationtechnique.

The ‘RadioResourceConfigDedicated’ IE is used to setup/modify/releasethe Radio Bearer, to change the MAC main configuration, to change theSemi-Persistent Scheduling (SPS) configuration and to change thededicated physical configuration.

The ‘RadioResourceConfigDedicated’ IE includes the‘measSubframePattern-Serv’ field that indicates the time domainmeasurement resource restriction pattern for serving cell measurement.In addition, the ‘RadioResourceConfigDedicated’ IE includes‘measSubframeCellList’ indicating the neighbor cell that is going to bemeasured by the UE and ‘measSubframePattern-Neigh’ indicating the timedomain measurement resource restriction pattern for neighbor cellmeasurement.

The time domain measurement resource restriction pattern that isconfigured for the measuring cell (including the serving cell and theneighbor cell) may indicate at least one subframe per radio frame forperforming the RSRQ measurement. The RSRQ measurement is performed onlyfor the subframe indicated by the time domain measurement resourcerestriction pattern that is configured for the measuring cell.

As such, a UE (e.g., 3GPP Rel-10) should measure the RSRQ only in theduration configured by the subframe pattern (‘measSubframePattern-Serv’)for the serving cell measurement and the subframe pattern(‘measSubframePattern-Neigh’) for the neighbor cell measurement.

Although the measurement in the pattern for the RSRQ is not limited, butit is preferable to be measured only in the pattern for the accuracyrequirement.

Massive MIMO

In a wireless communication system after LTE Release (Rel)-12, theintroduction of an active antenna system (AAS) is taken intoconsideration.

Unlike in an existing passive antenna system in which an amplifier andan antenna in which the phase and size of a signal may be adjusted havebeen separated, the AAS means a system in which each antenna isconfigured to include an active element, such as an amplifier.

The AAS does not require a separate cable, a connector, and otherhardware for connecting an amplifier and an antenna depending on use ofan active antenna and thus has high efficiency in terms of energy and anoperation cost. In particular, the AAS enables an advanced MIMOtechnology, such as the forming of an accurate beam pattern or 3-D beampattern in which a beam direction and a beam width have been taken intoconsideration, because the AAS supports an electronic beam controlmethod for each antenna.

Due to the introduction of an advanced antenna system, such as the AAS,a massive MIMO structure including a plurality of input/output antennasand a multi-dimensional antenna structure is also taken intoconsideration. For example, unlike in an existing straight-line antennaarray, if a 2-D antenna array is formed, a 3-D beam pattern may beformed by the active antenna of the AAS.

FIG. 11 is a diagram illustrating an example of a 2D active antennasystem having 64 antenna elements to which the present invention can beapplied.

As shown in FIG. 11, it is possible to consider a case where Nt=Nv·Nhantennas have a square shape with a general two-dimensional antennaarrangement.

Here, Nh denotes the number of antenna rows in the horizontal direction,and Nv denotes the number of antenna rows in the vertical direction.

If a 3-D beam pattern is used from a viewpoint of a transmissionantenna, the forming of a semi-static or dynamic beam in the verticaldirection of a beam in addition to the horizontal direction may beperformed. For example, an application, such as the forming of a sectorin the vertical direction may be taken into consideration.

Furthermore, from a viewpoint of a reception antenna, when a receptionbeam is formed using a massive reception antenna, an effect of a rise ofsignal power according to an antenna array gain may be expected.Accordingly, in the case of uplink, an eNB may receive a signaltransmitted by a UE through a plurality of antennas. In this case, thereis an advantage in that the UE can configure its own transmission powervery low by taking into consideration the gain of a massive receptionantenna in order to reduce an interference influence.

FIG. 12 illustrates a system having a plurality oftransmission/reception antennas through which an eNB or a UE is capableof three-dimensional (3-D) beamforming based on an AAS in a wirelesscommunication system to which an embodiment of the present invention maybe applied.

FIG. 12 is a diagram of the aforementioned example and illustrates a 3DMIMO system using a 2-D antenna array (i.e., a 2D-AAS).

Cell Coverage of Massive MIMO

A multiple antenna system, for example, a system having N transmissionantennas may perform beamforming so that received power is increased bya maximum of N times at a specific point, assuming that totaltransmission power is identically transmitted compared to a singleantenna system.

Even an eNB having multiple antennas, a channel that transfers a CRS, aPSS/SSS, a PBCH and broadcast information does not perform beamformingin a specific direction so that all of UEs within an eNB coverage areacan receive them.

In some cases, a PDSCH, that is, a channel that transfers unicastinformation to a specific UE, performs beamforming according to thelocation of a corresponding UE and link situation in order to improvetransmission efficiency. That is, the transmission data stream of thePDSCH is precoded in order to form a beam in a specific direction andtransmitted through multiple antenna ports. Accordingly, for example, iftransmission power of a CRS and transmission power of a PDSCH are thesame, received power of a precoded PDSCH beamformed toward acorresponding UE may be increased up to a maximum of N times compared toaverage received power of a CRS to a specific UE.

Up to now, in the LTE Rel-11 system, an eNB having a maximum of 8transmission antennas is taken into consideration. This means thatreceived power of a precoded PDSCH may be eight times greater thanaverage received power of a CRS. In the future, however, if the numberof transmission antennas of an eNB is 100 or more due to theintroduction of a massive MIMO system, a difference between receivedpower of a CRS and received power of a precoded PDSCH may be 100 timesor more. In conclusion, due to the introduction of the massive MIMOsystem, the coverage area of a CRS transmitted by a specific eNB and thecoverage area of a DM-RS-based PDSCH are not identical.

In particular, such a phenomenon may be significant if a difference inthe number of transmission antennas between two adjacent eNBs is great.A representative example includes an example in which a macro cellhaving 64 transmission antennas and a micro cell (e.g., a pico cell)having a single transmission antenna neighbor each other. A UE served inan initial deployment process of massive MIMO first expects that thenumber of antennas may be increased from many macro cells. Accordingly,in the case of a heterogeneous network in which a macro cell, a microcell and a pico cell are mixed, there is a great difference in thenumber of transmission antennas between adjacent eNBs.

For example, in the case of a pico cell having a single transmissionantenna, the coverage area of a CRS and the coverage area of a PDSCH arethe same.

In the case of a macro cell having 64 transmission antennas, thecoverage area of a PDSCH is greater than the coverage area of a CRS.Accordingly, if initial access and handover are determined based on onlyRSRP or RSRQ, that is, reception quality of the CRS, at the boundary ofthe macro cell and a pico cell, an eNB capable of providing the bestquality of the PDSCH may not be selected as a serving cell. As a simplesolution for this problem, PDSCH received power of an eNB having Ntransmission antennas may be assumed to be N times great, but such amethod is not the best solution if a case where the eNB cannot performbeamforming in all of directions as possible is taken intoconsideration.

Hereinafter, a CSI measurement and reporting operation method of aterminal (or UE) for reducing latency will be described.

It should be understood that the method described below may be appliednot only to systems such as 3D-MIMO and massive MIMO, but alsoextensively to an amorphous cell environment, and the like.

First, the 3D-MIMO system will be described briefly.

The 3D-MIMO system is one of optimal transmission systems suitable for asingle-cell 2D-AAS (adaptive antenna system) base station as shown inFIG. 12 based on the LTE standard (Rel-12), and the following operationmay be considered.

As shown in FIG. 12, an example of configuring CSI-RS ports from an8-by-8 (8×8) antenna array will be described. A total of 8-port(vertically precoded) CSI-RSs in a horizontal direction areconfigured/transmitted for each of eight antennas vertically, byconfiguring one precoded CSI-RS port to which UE-dedicated beamcoefficients optimized for a specific target UE are applied.

Thus, the UE may perform CSI feedback for the conventional 8-port.

Finally, a BS transmits (precoded) CSI-RS 8 ports to which a verticalbeam gain optimized for each individual UE (or a specific UE group) wasalready applied, to the UE.

Thus, since the UE measures a CSI-RS that has undergone a wirelesschannel, although the UE performs the same feedback scheme based on theconventional horizontal codebook, the UE may already obtain a verticalbeam gain effect of a wireless channel through a CSI measurement andreporting operation regarding the (vertically precoded) CSI-RS.

In this case, a method for determining a vertical beam optimized for anindividual terminal includes (1) a method of using the RRM report resultbased on a (vertically precoded) small-cell discovery RS (DRS) and (2) amethod of receiving, by the BS, a sounding RS (SRS) of a UE in anoptimal receiving beam direction and converting the receiving beamdirection into a DL optimum beam direction by channel reciprocity.

If the BS determines that the direction of the UE-dedicated best V-beamhas been changed due to mobility of the UE, the BS re-configures all theRRC settings related to the CSI-RS and an associated CSI processaccording to the conventional operation.

When the RRC reconfiguration process is performed in this manner,occurrence of latency at a RRC level (e.g., unit of tens to hundreds ofms) is inevitable.

In other words, in the network level, a target V-beam direction isdivided into, for example, four directions and 8-port CSI-RSs havingprecoding in each V-direction are transmitted at a correspondingtransmission resource position.

Also, since each UE must perform CSI measurement and reporting on aspecific CSI-RS setting among the 8-port CSI-RSs, when the targetV-direction is changed, the UE has no choice but to an RRCreconfiguration procedure with a network by the CSI-RS configuration tobe changed.

2D Planar Antenna Array Model

FIG. 13 shows an example of a polarization-based 2D planar antenna arraymodel.

That is, FIG. 13 illustrates an example of a 2D AAS (active antennasystem) having cross-polarization.

Referring to FIG. 13, the 2D planar antenna array model may berepresented by (M, N, P).

Here, M denotes the number of antenna elements having the samepolarization in each column, N denotes the number of columns in thehorizontal direction, and P denotes the number of dimensions ofpolarization.

In FIG. 13, for cross-polarization, P=2.

FIG. 14 shows an example of a model of transceiver units (TXRUs).

The TXRU model configuration corresponding to the antenna array modelconfiguration (M, N, P) of FIG. 14 may be expressed as (MTXRU, N, P).

In this case, MTXRU means the number of TXRUs existing in the samepolarization in the same row of 2D, and MTXRU<=M is always satisfied.

Also, the TXRU virtualization model is defined by a relationship betweensignals of the TXRUs and the signals of antenna elements.

Here, q is a transmission signal vector of M antenna elements having thesame polarization in the same column, w and W represent a wideband TXRUvirtualization weight vector and matrix, and x represents a signalvector of MTXRU TXRUs.

Specifically, FIG. 14A shows a TXRU virtualization model option-1(sub-array partition model) and FIG. 14B shows a TXRU virtualizationmodel option-2 (full connection model).

That is, the TXRU virtualization model is classified into a sub-arraymodel and a full-connection model according to correlation between theantenna elements and the TXRU, as shown in FIGS. 14A and 14B.

Also, mapping between CSI-RS ports and TXRUs may be 1-to-1 or 1-to-many.

In the case of the massive MIMO system using a 2D-AAS antenna structure,or the like, described above with reference to FIG. 12, the UE acquiresa CSI via a CSI-RS transmitted from the BS and, in order to report theobtained CSI to the BS, a large number of CSI-RS ports need to bedesigned.

That is, in the massive MIMO system, a new CSI-RS pattern having alarger number of ports such as a 12-port CSI-RS pattern, a 16-portCSI-RS pattern, and the like, and a configuration method are required tobe considered, compared with the conventional CSI-RS pattern of 1, 2, 4,and 8 ports.

The N-port CSI-RS pattern shown in this disclosure may be interpreted tohave the same meaning as an N-port CSI-RS resource.

Here, the N-port CSI-RS resource or N-port CSI-RS pattern is a resource(group) representing REs (or a group of REs) in which the CSI-RS istransmitted through N ports, and one or more N-port CSI-RS resources maybe present in one subframe or a plurality of subframes.

A plurality of N-port CSI-RS resources may be represented by an N-portCSI-RS resource pool.

For example, a 4-port CSI-RS resource includes 4 REs, and an antennaport number to which a CSI-RS is transmitted is mapped to each RE.

In order to effectively support closed-loop MIMO transmission in atransmitter (e.g., BS) having a large number of transmit antennaelements (e.g., MNP), such as the massive MIMO system, a Q-port CSI-RSpattern (e.g., Q<=MNP) should be set to the terminal.

The reason for this is that the UE must support an operation ofmeasuring the set Q-port CSI-RSs together and calculating and reportingthe CSI on the basis of the set Q-port CSI-RS together.

For example, the Q-port CSI-RS set to the UE may be a non-precodedCSI-RS.

The non-precoded CSI-RS may be expressed as type A or type B.

The non-precoded CSI-RS means a CSI-RS transmitted by a transmissionend, without applying beamforming thereto, and may generally have a formof transmitting each CSI-RS port having a wide beam width.

The conventional CSI-RS pattern (or CSI-RS resource) will be describedfurther with reference to FIGS. 15 and 16.

FIG. 15 shows an example of 8 port-CSI-RS resource mapping pattern.

That is, FIG. 15 shows a transmittable resource or resource pattern of aCSI-RS having 8 antenna ports in one resource block (RB) including 12subcarriers in the LTE(-A) system.

In FIG. 15, the differently shaded portions represent CSI-RS resources(or CSI-RS patterns 1510, 1520, 1530, 1540, and 1550), respectively.

That is, in FIG. 15, it may be seen that there are five CSI-RS resourcesor five CSI-RS patterns in one subframe.

Referring to FIG. 15, the CSI-RS for one port is spread over two OFDMsymbols and transmitted.

Two CSI-RSs share two REs, and two CSI-RSs shared in two REs may bedistinguished by using an orthogonal code.

In FIG. 15, REs represented by the numbers of ‘0’ and ‘1’ means two REsin which CSI-RS port 0 and 1 are transmitted.

In this disclosure, for convenience of description, the expression suchas CSI-RS port 0, 1 is used. However, in order to distinguish from othertypes of RS such as CRS and UE-specific RS, the CSI-RS port 0, 1 may beexpressed in an index form such as CSI-RS port 15, 16, and so on.

The CSI-RS may also be set to have ports 1, 2, and 4, in addition toport 8.

Referring to Table 3 and FIG. 15, common to frame structure type 1 (FDDmode) and type 2 (TDD mode) of the LTE system, the 8-port CSI-RSs haveonly 5 CSI-RS transmission patterns (or 5 CSI-RS resources) in onesubframe.

FIG. 16 shows another example of CSI-RS resources.

That is, FIGS. 16A, 16B, and 16C show examples of 2-port, 4-port, and8-port CSI-RS transmission patterns, respectively.

In FIGS. 16A, 16B, and 16C, the differently shaded portions representone CSI-RS resource or one CSI-RS pattern.

Hereinafter, a method of configuring a new CSI-RS resource (or a newCSI-RS pattern) in relation to CSI-RS transmission using antenna portsmore than 8 ports proposed in the present disclosure will be describedin detail with reference to the related drawings.

First Embodiment

A first embodiment provides a method of configuring a new CSI-RSresource in a normal cyclic prefix (CP) and a method of mapping anantenna port number to each resource element (RE) in a CSI-RS resource.

Hereinafter, a method of configuring a new CSI-RS pattern (or a newCSI-RS resource) in a massive MIMO system proposed in the presentspecification, using a 12-port CSI-RS pattern and a 16-port CSI-RSpattern as a typical example, and a method for mapping an antenna portnumber to each CSI-RS pattern will be described.

FIG. 17 shows an example of a 12-port CSI-RS resource structure proposedin this disclosure.

That is, FIG. 17 shows design of a 12-port new CSI-RS pattern(hereinafter referred to as ‘new CSI-RS pattern’ for convenience ofdescription, and the method proposed in FIG. 17 may also be applied tocases other than 12-port).

In the new CSI-RS pattern design, a new CSI-RS pattern including atleast one of the following technical characteristic factors (1) to (3)may be designed.

The technical characteristic factors (1) to (3) will be described one byone.

(1) A new CSI-RS pattern is created in the form of combining some oflegacy 1, 2, 4, and 8 port CSI-RS patterns.

New CSI-RS patterns 1710 and 1720 illustrated in FIG. 17 represent a newCSI-RS pattern designed (or created) in the form of combining one 8-portCSI-RS pattern and one 4-port CSI-RS pattern.

In this manner, in the case of limiting the new CSI-RS pattern to theform of a combination of legacy CSI-RS patterns (or legacy CSI-RSresources), legacy impact may be advantageously minimized by setting aspecific ZP CSI-RS resource(s) supported by the current standard tolegacy terminals.

(2) Rule for CSI-RS port numbering within new CSI-RS pattern

Rule for CSI-RS port numbering may be carried out through 1) to 3) asfollows.

1) As illustrated in FIG. 17, first, port 0 and 1 (actually, a startingpoint of port numbering may be 15, rather than 0, using port 15, 16,etc.) may be mapped to REs corresponding to the lowest (or highest)subcarrier index.

In FIG. 17, ports 0 and 1 may be mapped to different (OFDM) symbols, andports 0 and 1 may be CDM-ed to each other and mapped to two REs.

2) Next, ports 2 and 3 may be mapped to REs in a CSI-RS resource asfollows.

When a next subcarrier index adjacent to positions of REs of the ports 0and 1 is occupied by (i) the new CSI-RS pattern to which the port 0 and1 are mapped and (ii) the contiguously adjacent REs is a subgroup #1(1711) of the new CSI-RS pattern, if a subgroup #2 (1712) of the newCSI-RS pattern not adjacent to the subgroup #1 exists, ports 2 and 3 arepreferentially mapped to REs corresponding to a lowest (or highest)subcarrier index of the subgroup #2.

If the port numbers are mapped to all the REs corresponding to thelowest (or highest) subcarrier index for each subgroup, ports 2 and 3are mapped to REs corresponding to a second lowest (or highest)subcarrier index in the subframe #1 (1711) in which mapping was firststarted.

In this manner, port indexing is performed first by the subframes inturn, and port indexing is performed in ascending (or descending) orderof subcarrier index in each subgroup.

FIG. 17 shows an example in which antenna port numbering is appliedaccording to the rule discussed in 2).

3) Like the port numbering rule in FIG. 17, the new CSI-RS pattern maybe limitedly designed to have the same number of CSI-RS ports for eachsubgroup.

That is, as illustrated in FIG. 17, the 12-port CSI-RS may be dividedinto two subgroups and each subgroup may include six CSI-RS ports.

(3) All CSI-RS ports belonging to one New CSI-RS pattern are present inL consecutive (OFDM) symbols.

In FIG. 17, it may be seen that a total of 12 CSI-RS ports are arrangedin two consecutive symbols (L=2 consecutive (OFDM) symbols) for each NewCSI-RS pattern.

Alternatively, a new CSI-RS pattern may be designed (or created) bycombining with REs corresponding to the CSI-RS pattern Y in FIG. 17, byallowing up to L=5.

In this case, CSI-RS ports existing in the same one new CSI-RS patternmay be separated by a maximum of 4 OFDM symbols.

Thus, in this case, there may be a disadvantage that an influence ofphase drift is larger in channel measurement of the UE than the newCSI-RS pattern design corresponding to L=2.

However, in the case of designing a new CSI-RS pattern using up to fiveconsecutive OFDM symbols, flexibility of the design of the new CSI-RSpattern is increased accordingly.

Thus, using up to five consecutive OFDM symbols has the advantage ofproviding greater flexibility in configuring the CSI-RS at the networkend.

Alternatively, a new CSI-RS pattern may be designed by combining withthe REs corresponding to the CSI-RS pattern X in FIG. 17, allowing up toL=6 similarly to the case of L=5.

As described in (1) above, the new CSI-RS pattern may be limited only toa combination of legacy CSI-RS patterns, but the present invention isnot limited thereto and a method for extendedly designing the new CSI-RSpattern in the form of including RE(s) other than the legacy CSI-RSpattern.

In this case, the L value described in (3) may be greater than 2, andREs without indications in FIG. 17, that is, some of the PDSCH REs, maybe designed as RE(s) which belong to the new CSI-RS pattern.

In this case, since the REs are not covered by the legacy ZP (ZeroPower) CSI-RS resources, a new ZP CSI-RS resource capable of coveringthe REs may be required to be designed together.

That is, among enhanced UEs, when a UE receives a PDSCH from a BS, aseparate ZP CSI-RS resource for covering the REs occupied by the newCSI-RS pattern should be supported to enable rate matching of positionsof the REs according to the new CSI-RS pattern.

That is, the UE may be set in the separate ZP CSI-RS resource from theBS through RRC signaling and apply the set ZP CSI-RS resource to PDSCHRE mapping (rate matching).

The UE, which is set in the new RS pattern designed according to therules of (1) to (3) above (through RRC signaling), may measure CSI-RSports corresponding to the new RS pattern simultaneously when set in thenew RS pattern, and additionally set in mapping information together tocalculate a CSI on the basis of the measured CSI-RS ports.

The mapping information indicates information related to in which orderthe CSI-RS port numbering in the new RS pattern is mapped to the antennaconfiguration of the actual transmission antenna.

For example, even the same 12-port CSI-RS pattern may follow a TXRUconfiguration in the form of FIG. 18A or a TXRU configuration in theform of FIG. 18B.

Therefore, in order to inform the UE whether the 2D antenna array formis the form of FIG. 18A or the form of FIG. 18B, the BS may inform theUE about at least one of parameters such as the number (Na) of columnsof the 2D antenna array, the number (Ma) of rows, the number (P) ofpolarizations, and the like, through higher-layer signaling.

Here, these parameters may be included in NZP CSI-RS configurationinformation.

Alternatively, these parameters, basically related to CSI reporting ofthe UE, may be transmitted by the BS to the UE through (or inconjunction with) a specific CSI process configuration including aspecific NZP CSI-RS configuration in which the corresponding new RSpattern is set.

That is, the specific CSI process configuration may include ‘parametersallowing the UE to recognize a specific CSI-RS port mapping pattern’such as Na, Ma, P, and the like.

FIG. 18 shows examples of a 2D antenna array model to which the methodproposed in this disclosure may be applied.

For example, when the UE which receives the 12-port CSI-RS configurationfrom the base station is set in Na=3, Ma=2, and P=2 together, the UEperforms CSI derivation on the assumption of the TXRU configuration (orCSI-RS port distribution/configuration as illustrated in FIG. 18A.

If the UE is set in Na=2, Ma=3, and P=2 together with the 12-port CSI-RSconfiguration, the UE performs CSI derivation on the assumption of theTXRU configuration (or CSI-RS port distribution/configuration) asillustrated in FIG. 18B.

Also, when the CSI-RS port numbering is given in the form illustrated inFIG. 17, the UE may be set such that the CSI-RS port numbers are mappedfirst in rows (or first in columns) in ascending order (or descendingorder), starting from a specific corner (e.g., the lowest left) on theTXRU configuration which may be assumed in the form of FIG. 18A or 18B.

Here, regarding different polarizations, when the ‘row first (or columnfirst)’ mapping is performed, sequential mapping is performed for eachpolarization index at the same column (or row) index and mapping may beperformed in a next column (or row) index.

Alternatively, the port numbering pattern itself may be explicitly RRCsignaled in a specific form (e.g., bitmap) to the UE.

An advantage of the 12-port CSI-RS pattern of FIG. 17 is that networkflexibility may be increased when it is set together with the legacyCSI-RS pattern in the same subframe.

For example, when a specific cell or TP (transport point) A transmitsonly ‘12-port new CSI-RS pattern #1” in FIG. 17, any other cell (or TP)(or the same cell or TP A additionally) may selectively transmit atleast any one of the legacy 1, 2, or 4 port CSI-RS patterns in REs of anempty ‘12-port new CSI-RS pattern #2’.

This is because no overlap occurs between the CSI-RS patterns.

However, the design method for the 12-port CSI-RS is not limited theretoand various other additional design methods may be present.

That is, for the 12-port CSI-RS pattern, at least one of various methodsas shown in FIG. 19, or the like, including FIG. 17 may be defined orset.

Also, the BS may inform the UE about which of CSI-RS patterns the UEshould assume to receive a CSI-RS through higher-layer signaling andperform CSI derivation therethrough.

FIG. 19 shows another example of a 12-port CSI-RS resource mappingpattern proposed in this disclosure.

FIG. 19 shows a case where the numbers of ports of each subgroup withina new CSI-RS pattern are different.

That is, the number of ports in one subgroup is 2 and the number ofports in another subgroup is 4.

FIG. 20 shows another example of a 12-port CSI-RS resource mappingpattern proposed in this disclosure.

FIG. 20 shows a case where a new CSI-RS pattern has three subgroups andeach subgroup includes 4 ports.

A method of designing a 16-port CSI-RS pattern using the port numberingapplication rules of (1) to (3) discussed above will be described withreference to FIGS. 21 and 22.

FIGS. 21 and 22 show examples of a 16-port CSI-RS pattern proposed inthis disclosure.

Referring to FIGS. 21A and 21B, two ‘16-port new CSI-RS patterns’ may berepresented as 16-port new CSI-RS pattern #1 and 16-port new CSI-RSpattern #2, respectively.

Here, similarly, the 16-port CSI-RS pattern may be expressed or referredto as a 16-port CSI-RS resource.

As shown in FIGS. 21A and 21B, in the case 16-port, when a pattern #12110 and a pattern #2 2120 are simultaneously configured/transmitted inthe same subframe, they may overlap in some RE positions.

Thus, preferably, when the specific cell/TP A transmits the pattern #1of FIG. 21A, another cell/TP configure/transmits a legacy CSI-RS usingpositions of legacy CSI-RS patterns indicated by ‘Z’ and/or legacypatterns indicated by ‘X’ and ‘Y’ in the corresponding subframe, ratherthan configuring/transmitting another 16-port CSI-RS.

In relation to the description of (1) discussed above, one example ofthe CSI-RS (resource mapping) pattern of FIG. 21 is a combination of two8-port CSI-RS patterns and it may be interpreted as a case where one newCSI-RS pattern is designed.

Also, in relation to the description of (3) discussed above, one exampleof the CSI-RS resource mapping pattern shown in FIG. 21 is shows a casewhere a total of 16 CSI-RS ports for each new CSI-RS pattern are alldisposed in L=2 consecutive (OFDM) symbols.

Here, since there is a disadvantage in that two new patterns cannotcoexist in one subframe in FIG. 21, it may be defined/configured suchthat a specific (at least) one new pattern has L>2 in such a form as inFIG. 22.

Similarly, in FIG. 22, as an example of CSI-RS port numbering in FIG.22, port numbering may be defined/configured in various forms includingthe above-mentioned methods (1) to (3).

For example, in FIG. 22, REs corresponding to ports 4 and 5 of newpattern #2 may be started to be mapped to ports 0 and 1.

This means a rule in which mapping is not performed in ascending orderof the OFDM symbol index but ports 0 and 1 is started to be first mappedin ascending order of the sub carrier index.

Also, in another port numbering method for the new CSI-RS pattern, itmay be defined/configured such that mapping is performed by firstfilling port indices within the same subgroup in ascending (ordescending) order and mapping is subsequently performed by filling portindices within a next subframe consecutively in ascending (ordescending) order, rather than port indices are assigned first bysubgroups.

Also, in the example of FIG. 22, new CSI-RS patterns may be obviouslydesigned in the form of port numbering mapping using positions of “REsused for X-indicated legacy CSI-RS patterns”, instead of REs indicatedby ports 4, 5, 6, 7, 12, 13, 14, and 15 of the new pattern #2.

In this case, L=6 may be obtained.

Second Embodiment

A second embodiment provides a new CSI-RS resource mapping pattern in anextended cyclic prefix (CP).

In the first embodiment, the embodiments assuming the case of the normalCP have been discussed based on the 12-port and 16-port new CSI-RSpattern design.

Hereinafter, in the second embodiment, the case of the extended CP inthe form of including the principle of the proposed method described inthe first embodiment will be described.

FIG. 23 is a view illustrating another example of a 8-port CSI-RSpattern proposed in this disclosure.

In detail, FIG. 23 illustrates a transmittable pattern of CSI-RS having8 antenna ports in a subframe to which the extended CP is applied.

In FIG. 23, an orthogonal cover code (OCC) is applied to two OFDMsymbols of a CSI-RS, and two CSI-RS antenna ports are differentiated ina CDM manner.

Thus, two CSI-RSs share two REs and are distinguishably transmitted byOCCs.

In FIG. 23, the REs expressed by the numbers 0 and 1 means two REs inwhich CSI-RS ports 0 and 1 are transmitted.

For purposes of description, the expression such as CSI-RS port 0, 1 isused, and CSI-RS port 0, 1, etc., may be represented such as CSI-RS port15, 16 for distinguishing from other types of RS such as CRS and otherUE-specific RS.

The CSI-RSs may be configured to have 1, 2, and 4 antenna ports inaddition to the 8 antenna ports.

FIG. 24 shows an example of various CSI-RS patterns proposed in thisdisclosure.

FIG. 24 shows CSI-RS patterns for cases where CSI-RS antenna ports are1, 2, and 4 ports in a subframe to which the extended CP is applied.

In consideration of the conventional legacy CSI-RS pattern position asshown in FIG. 24, it may be seen that the CSI-RS pattern designprinciples such as the methods (1) to (3) described in the firstembodiment (the case of normal CP) may be extendedly applied in a statein which only the legacy pattern positions are different.

For example, when 16-port new CSI-RS pattern is defined/configured inthe case of the extended CP, 16 ports may be created by combining twolegacy 8-port patterns in FIG. 24.

Also, the CSI-RS port numbering may be defined/configured by applyingthe specific port numbering rule of the first embodiment.

Of course, in configuring the 16-port CSI-RS pattern, some ports may bedesigned by partially combining PDSCH REs other than the legacy pattern.

In addition, in order to configure a 12-port CSI-RS pattern, the 12-portCSI-RS pattern may be defined/configured in the form of excluding fourspecific port positions in the 16-port CSI-RS pattern.

In this case, the four excluded port positions may be defined to matchone specific legacy 4-port pattern.

The reason for defining in this manner is that the numbers of CSI-RSpatterns that may be configured/transmitted by cells/TPs in the samesubframe do not overlap as possible and that the CRI-RS patterns may betransmitted along with the legacy CSI-RS port pattern.

For example, it is assumed that a 16-port new CSI-RS pattern is definedby combining two legacy 8-port CSI-RS patterns in FIG. 24.

Here, a scheme of defining/configuring a 12-port new CSI-RS pattern inthe form of excluding 4 RE positions corresponding to one specific4-port legacy pattern shown in FIG. 24 from the 16-port new CSI-RSpattern is applicable.

Here, there may be various methods for excluding the “one specific4-port legacy pattern”.

That is, in order to increase network flexibility, rather than definingonly a 12-port pattern #1 by excluding only one specific 4-port legacypattern, up to 12-port pattern #n may be defined by defining another12-port pattern #2 by excluding another specific 4-port legacy pattern.

A method of selectively configuring in which number of pattern isconfigured by Ues, through an indicator, or the like, may also beapplied.

The UE measures a channel for a CSI regarding the specific 12-portpattern #i (i=1, 2, . . . , or n) set as described above and performsCSI reporting to the BS.

Third Embodiment

The third embodiment provides a method of configuring new CSI-RSresources by aggregating a plurality of (existing) CSI-RS resources.

For example, a 12-port CSI-RS resource may be configured by aggregatingthree 4-port CSI-RS resources.

Alternatively, a 16-port CSI-RS resource may be configured byaggregating four 4-port CSI-RS resources.

Alternatively, the 16-port CSI-RS resource may be configured byaggregating two 8-port CSI-RS resources.

In detail, a method of configuring a new CSI-RS pattern proposed in thethird embodiment may be defined in a form in which at least one of theprinciples of the following methods 1 to 4 is applied.

(1) Method 1

It is defined that a new CSI-RS (resource) is always configured in theform of multiple aggregation of specific existing X-port CSI-RSresources.

In one example, X=4 may be fixed.

When X is fixed to ‘4’, the new CSI-RS configuration has expandabilitythat it may be configured to 4-port, 8-port, 12-port, 16-port, 20-portand the like.

Also, when X is fixed to ‘2’ (X=2), the new CSI-RS resource may beconfigured to have a port number that is a multiple of 2.

When the New CSI-RS configuration is provided in such a form that theX-port CSI-RS resources are Y multiple aggregated, a total of XY portsexists

Port numbering rules for a total of XY number of antenna ports mayfollow the scheme of 1) option 1 or 2) option 2.

For the purposes of description, it is assumed that CSI-RS resource #1,CSI-RS resource #2, . . . , CSI-RS resource #Y are aggregated together,and port numbering in the CSI-RS resources is given 0, 1, . . . , AndX−1, respectively.

Here, the port numbering in each CSI-RS resource is in the form of 15,16, . . . , 15+X−1, and a starting point of the port number is notactually 0 and may be 15 or any other value.

1) Option 1

Port numbering for a total XY number of ports (0, 1, . . . , XY−1) maybe determined as follows.

Similarly, a starting point of port number may not be 0.

Among the total of XY number of ports, {0, 1, . . . , X−1} issequentially mapped to X number of {0, 1, . . . , X−1} ports within aCSI-RS resource #1, respectively.

Subsequently, {X, X+1, . . . , 2X−1} is sequentially mapped to X numberof {0, 1, . . . , X−1} ports within a CSI-RS resource #2.

In this manner, ports are continuously sequentially connected to bemapped in ascending order (or descending order) of CSI-RS resourceindices, and {(Y−1)X, (Y−1)X+1, . . . , YX−1}, a final X number of portindices, are sequentially mapped to X number of {0, 1, . . . , X−1} portof CSI-RS resource #Y

Regarding the total of mapped port indices {0, 1, . . . , XY−1}, the UEperforms CSI derivation by applying a corresponding codebook through aCSI process configuration (or associated CSI feedback configuration).

2) Option 2

Port numbering for a total of XY ports (0, 1, . . . , XY−1) isdetermined as follows.

Among the total of XY ports, {0, 1, . . . , Y−1} are sequentially mappedto port Os within CSI-RS resource #1, #2, . . . , #Y.

Subsequently, {Y, Y+1, . . . , 2Y−1} are sequentially mapped to port 1swithin CSI-RS resource #1, #2, . . . , #Y.

Continued in this manner, the last Y port indices {(X−1) Y, (X−1) Y+1, .. . , XY−1} are sequentially mapped to port (X−1)x within CSI-RSresource #1, #2, . . . , #Y.

The UE performs CSI derivation by applying a corresponding codebook tothe total port indices {0, 1, . . . , XY−1} as mapped through a CSIprocess configuration (or associated CSI feedback configuration).

(2) Method 2

In the situation in which the method 1 is applied as described above, itmay be extendedly defined/configured such that, after the Y multipleX-port CSI-RS resources are aggregated, one additional A-port (0<A<X)CSI-RS resource may be further aggregated, as an exceptional additionalcondition.

For example, in case where X=4, Y=3 and A=2, since three 4-port CSI-RSresources are aggregated, when one 2-port CSI-RS resource is furtheraggregated in a total of 12-port CSI-RS state, a total of 14-port CSI-RSresources may be configured.

This is advantageous in that it is possible to add a specific A-portnumber that is smaller than X-port by extending from limiting toaggregation only in units of X-port CSI-RS resources.

As a result, if a 14-port CSI-RS resource is to be configured, it may beconfigured by including a total of four CSI-RS resources (threeX-ports+one A-port CSI-RS resource).

In this case, Option 1 and Option 2 in Method 1 may be partiallyextended as described below.

1) Option 1′

Option 1 (or Option 2) scheme in method 1 is applied only to X-portCSI-RS resources preferentially in the same manner.

That is, {0, 1, . . . , XY−1} port is first mapped, and then, {XY,XY+A−1}, A (e.g., A=2) number of addition ports, are respectivelysequentially mapped to {0, . . . , A−1} ports within the added A-portCSI-RS resources.

2) Option 2′

According to the option 2 scheme in the method 1, when a total of YX-port CSI-RS resource indices are referred to as CSI-RS resource #1,#2, . . . , #Y, the added one A-port CSI-RS resource index may bereferred to as #(Y+1).

Also, preferentially, the port 0s in each CSI-RS resource are mappedfirst in ascending (or descending) order of the CSI-RS resource index.

Next, the port 1s in each CSI-RS resource are mapped in ascending (ordescending) order of the CSI-RS resource index, and here, if there is aspecific CSI-RS resource without port 1, the corresponding port isskipped in mapping.

In this manner, every port mapping is performed by repeating theoperation on the next port 2, and then on the next port 3 (as long asone CSI-RS resource index including the corresponding port remains).

(3) Method 3

The exceptional operation described in the method 2 may be generalizedor extendedly applied as follows.

That is, after Y multiple X-port CSI-RS resources are aggregated, oneA-port (0<A<X) CSI-RS resource may be additionally aggregated, and here,one more B-port (0<B<A) CSI-RS resource may be further aggregated.

Further, it is possible to extendedly define/configure such that CSI-RSresources of a smaller port unit may be additionally continuously setsuch that one C-port (0<C<B) CSI-RS resource is further aggregated inaddition.

In applying the method 1, the method 2 and the method 3 described above,the CRI-RS resources denoted in the form of CSI-RS resource #1 andCSI-RS resource #2 may refer to indices to which CSI-RS resource ID onRRC signaling is assigned or refer to indices sequentially assigned by#1, #2, etc., from the front, after the CSI-RS resource IDs assignedthrough RRC signaling are aligned in ascending order.

Hereinafter, a method of configuring a new CSI-RS resource byaggregating a plurality of legacy CSI-RS resources and a method ofperforming antenna port numbering on CSI-RS RE(s) within a CSI-RSresource using a CSI-RS configuration (index) will be described indetail through a fourth embodiment.

Here, the legacy CSI-RS resource refers to 1-port, 2-port, 4-port, and8-port CSI-RS resources, and a new CSI-RS resource refers to a CSI-RSresource regarding ports (e.g., 12-port, 16-port, etc.) greater than8-port.

As described above, a CSI-RS resource represents a pattern of a resourcein which a CSI-RS is transmitted. Generally, one X-port CSI-RS resourcemay include REs corresponding to the X number of ports.

Also, a plurality of CSI-RS resources may be referred to as a CSI-RSresource pool.

Fourth Embodiment

In the fourth embodiment, a method for an antenna port numbering rulefor CSI-RS resources (for example, three 4-port resources in the case of12-port and two 8-port resources in the case of 16-port) using themethod 1 to the method 3 described above.

That is, the fourth embodiment provides a rule (or method or mapping)for positions of the RE(s) in which the CSI-RS is transmitted in eachCSI-RS resource and the antenna port numbering for the correspondingRE(s).

That is, antenna port numbering rule may be defined/configured byapplying CSI-RS configuration number (or index) related to CSI-RS REpositions to which the X antenna ports are mapped in informationconfigured through (X-port) CSI-RS resource #i (i=0, 1, 2, . . . ),regardless of a CSI-RS resource ID set by the BS to the UE through RRCsignaling (e.g., CSI-RS Config.).

Here, (X-port) CSI-RS resources #0, #1, #2, etc. include REs mapped to Xantenna ports, respectively.

The CSI-RS configuration number (or index) indicates the ‘CSI referencesignal configuration’, which is the leftmost column of Table 3 and Table4 discussed above.

Here, the index of the CSI-RS configuration in Table 3 and Table 4 isinformation indicating a starting point of an RE in which the CSI-RS istransmitted in the CSI-RS resource.

For example, it is assumed that there are Y number of CSI-RS resourcesthat are configured together for the UE in the same CSI process.

After the ‘CSI reference signal configuration’ numbers regarding the REpositions respectively indicated in CSI-RS resources are aligned inascending order (or descending order), the antenna port numbering ruleof the method 1 to method 3 is applied.

In this case, the forms of CSI-RS resources #1 and #2 represented in theabove-mentioned method 1 to method 3 are not the CSI-RS resource IDs onRRC signaling but ‘CSI reference signal configuration’ numberscorresponding to the CSI-RS reference indices re-aligned (in ascendingor descending order).

In this case, the antenna port numbering rule may be applied to eachCSI-RS resource by regarding that the CSI-RS resource #1, #2, etc.,correspond in order in which ‘CSI reference signal configuration’numbers are set/provided on RRC signaling configuration, without anoperation of aligning the ‘CSI reference signal configuration’ numbersin ascending (or descending) order.

For example, when X=4 (X is the number of antenna ports) and Y=3 (Y isthe number of CSI-RS resources), “CSI reference signal configuration”number may be set for three (Y=3) CSI-RS resources through RRC signaling(e.g., CSI-RS ConFIG. IE).

In this case, it is assumed that the CSI-RS configuration numbers are 2,6, and 4, respectively.

In this case, considering that the CSI-RS resource #1, the CSI-RSresource #2, and the CSI-RS resource #3 respectively correspond to ‘CSIreference signal configuration’ number 2, 6, 4, in the above-describedmethods (Method 1 to Method 3), the aforementioned antenna portnumbering rule may be applied.

An example of RRC signaling may be CSI-RS ConFIG. IE (InformationElement), and an example of a format thereof is shown in Table 6 belowand the parameters of Table 6 are shown in Table 7.

TABLE 6 -- ASN1START CSI-RS-ConfigNZP-r11 ::= SEQUENCE {  csi-RS-ConfigNZPId-r11   CSI-RS-ConfigNZPId-r11,  antennaPortsCount-r11   ENUMERATED {an1, an2, an4, an8},  resourceConfig-r11   INTEGER (0..31),   subframeConfig-r11   INTEGER(0..154),   scramblingIdentity-r11   INTEGER (0..503),  qcl-CRS-Info-r11 SEQUENCE {     qcl-ScramblingIdentity-r11 INTEGER(0..503),     crs-PortsCount-r11 ENUMERATED {n1, n2, n4, spare1},    mbsfn-SubframeConfigList-r11 CHOICE {         release   NULL,        setup SEQUENCE {           subframeConfigList   MBSFN-SubframeConfigList         }     } OPTIONAL   -- Need ON   }OPTIONAL,   -- Need OR   ...,   [[  eMIMO-Info-r13   CHOICE {      release   NULL,       setup SEQUENCE {        nzp-resourceConfigList-r13 SEQUENCE (SIZE (2..8)) OFResourceConfig-r13,         cdmType ENUMERATED {cdm2, cdm4}   OPTIONAL -- Need OR       }     } OPTIONAL   -- Need ON   ]] }ResourceConfig-r13 ::= INTEGER (0..31) -- ASN1STOP

TABLE 7 CSI-RS-ConfigNZP field descriptions antennaPortsCount Parameterrepresents the number of antenna ports used for transmission of CSIreference signals where an 1 corresponds to 1, an2 to 2 antenna portsetc. see TS 36.211 [21, 6.10.5] cdmType EUTRAN configures this fieldonly for CSI processes that include eMIMO-Type set to nonPrecoded.qcl-CRS-Info : Indicates CRS antenna ports that is quasi co-located withthe CSI-RS antenna ports, see TS 36.213 [23, 7.2.5] EUTRAN configuresthis field if and only if the UE is configured with qcl-Operation set totypeB. resourceConfig : Parameter: CSI reference signal configuration,see TS 36.211 [21, table 6.10.5.2-1 and 6.10.5.2-2]. subframeConfig :Parameter: I_(CSI-RS) , see TS 36.211 [21, table 6.10.5.3-1].scramblingIdentity : Parameter: Pseudo-random sequence generatorparameter, n_(ID), see TS 36.213 [23, 7.2.5].

The antenna port numbering method in each CSI-RS resource (#1, #2, #3,etc.) may be applied according to option 1 described above.

First, an antenna port mapped to the CSI-RS resource #1 may be (0, 1, 2,3) or (15, 16, 17, 18), an antenna port mapped to CSI-RS resource #2 maybe (4,5,6,7) or (19,20,21,22), and an antenna port mapped to the CSI-RSresource #3 may be (8, 9, 10, 11) or (23, 24, 25, 26).

Also, positions of REs to which the antenna ports 0 (or 15), 4 (or 19),or 8 (or 23) are mapped may be determined by the CSI-RS configurationnumber (or index) corresponding to each CSI-RS resource.

The above-described antenna port mapping rule for each CSI-RS resourcemay be defined by Equation (13) below.

$\begin{matrix}{p = \left\{ \begin{matrix}{p^{\prime} + {\frac{N_{ports}^{CSI}}{2}i}} & {{{for}\mspace{14mu} p^{\prime}} \in \left\{ {15,\ldots \mspace{14mu},{15 + {N_{ports}^{CSI}/2} - 1}} \right\}} \\{p^{\prime} + {\frac{N_{ports}^{CSI}}{2}\left( {i + N_{res}^{CSI} - 1} \right)}} & {{{for}\mspace{14mu} p^{\prime}} \in \begin{Bmatrix}{{15 + {N_{ports}^{CSI}/2}},\ldots \mspace{14mu},} \\{15 + N_{ports}^{CSI} - 1}\end{Bmatrix}}\end{matrix} \right.} & \left\lbrack {{Equation}\mspace{14mu} 13} \right\rbrack\end{matrix}$

Here, i denotes the CSI-RS resource number and may have a value of i∈{0,1, . . . , N_(res) ^(CSI)−1}.

Also, the antenna port p may be determined as p=iN_(ports) ^(CSI)+p′ andp′ may have a value of p′∈{15, 16, . . . , 15+N_(ports) ^(CSI)−1}.

Here, the specific ‘CSI reference signal configuration’ number (e.g.,=2) may be included in the legacy CSI-RS resource configuration.

That is, according to the RRC signaling structure, a specific one (e.g.,it may be the first 2 or the last 4) of the ‘CSI reference signalconfiguration’ numbers 2, 6, and 4 may be provided through informationin a legacy (default) CSI-RS resource configuration RRC message (e.g.,CSI-RS ConFIG. IE).

For example, the specific CSI reference signal configuration number maybe provided through resourceConfig-r11 in CSI-RS-ConfigNZP-r11 in Table6.

Also, RRC signaling may be designed such that the other CSI referencesignal configuration numbers are additionally provided to the UE asadditional configuration number related information.

For example, the remaining CSI reference signal configuration numbersmay be provided through nzp-resourceConfigList-r13 andresourceConfig-r13 in Table 6.

Here, the specific ‘CSI reference signal configuration number (e.g.,=2)’ provided through the legacy (default) CSI-RS resource configurationmay be first matched to the CSI-RS resource #1 or first matched toCSI-RS resource #3.

In this regard, even when the BS transmits signaling to the UE throughanother RRC container according to a specific RRC message deliverystructure, there should be no ambiguity between the BS and the UE.

Therefore, a method by which 1-to-1 matching between the set ‘CSIreference signal configuration’ numbers and the CSI-RS resource #1, #2,#3, . . . in the aforementioned methods are clearly recognized by thespecific determined order (or rule) is defined.

First, a case where the specific ‘CSI reference signal configuration’number provided through legacy (default) CSI-RS resource configuration(information element) is matched to the lowest CSI-RS resource index(e.g.: CSI-RS resource #1) will be described.

For example, CSI-RS resource #1 may correspond to“resourceConfig-r11INTEGER (0 . . . 31)” configuration value indicatedin (legacy) “csi-RS-ConfigNZPld-r11” within a specific “CSI-Process-r11”configuration.

Also, CSI-RS resource #2 may correspond to a“ResourceConfig-r13::=INTEGER (0 . . . 31)” configuration valueindicated in a first “NZP-ResourceConfig-r13” in additionalconfiguration information expressed by“nzp-resourceConfigList-r13SEQUENCE SIZE (1 . . . 2) or (2 . . . 8)) OFNZP-ResourceConfig-r13” of “CSI-RS-ConfigNZP-EMIMO-r13”.

Also, CSI-RS resource #3 may correspond to “ResourceConfig-r13::=INTEGER (0 . . . 31)” configuration value indicated in a second“NZP-ResourceConfig-r13” in the additional configuration informationexpressed by “nzp-resourceConfigList-r13 SEQUENCE (SIZE (1 . . . 2)) OFNZP-ResourceConfig-r13” of “CSI-RS-ConfigNZP-EMIMO-r13”

It is needless to say that the above method may be applied to theantenna port mapping method for 16-port CSI-RS resources in the samemanner.

That is, the present invention may be applied to a method of mapping anantenna port to each CSI-RS resource in the structure of X=8 (X is thenumber of antenna ports) and Y=2 (Y is the number of CSI-RS resources)in the same manner.

Table 8 below summarizes the case where the legacy (default) describedabove corresponds to the first. In Table 8, the case of normal CP istaken as an example.

TABLE 8 Number of CSI-RS configured CSI-RS 4 (port), RRC config- Normalsignaling uration Antenna subframe (e.g.: CSI-RS number port n_(s)CSI-RS resource (index) number (k',l') mod2 Config. IE) #1 2 (0, 1, 2,3) (9, 2) 1 resourceConfig-r11 or INTEGER (15, 16, 17, 18) indicated inCSI-RS-ConfigNZ Pld-r11 #2 6 (4, 5, 6, 7) (10, 2) 1 resourceConfig-r13or INTEGER (19, 20, 21, 22) indicated in NZP- ResourceConfig-r13 #3 4(8, 9, 10, 11) (9, 5) 1 resourceConfig-r13 or INTEGER (23, 24, 25, 26)indicated in NZP- ResourceConfig-r13

In Table 8, k′ denotes a sub-carrier index in a resource block, l′denotes an OFDM symbol index in a slot, and ns denotes a slot in asubframe.

The CSI-RS configuration number (or index) in Table 8 will be referredto Tables 3 and 4 above.

Next, a case where a specific ‘CSI reference signal configuration’number provided through legacy (default) CSI-RS resource configurationcorresponds to the highest CSI-RS resource index (CSI-RS resource #3)will be described.

For example, the CSI-RS resource #3 in the above-mentioned methods(method 1 to method 3) may correspond to “ResourceConfig-r13 ::=INTEGER(0 . . . 31)” configuration value indicated in a first“NZP-ResourceConfig-r13” of the additional configuration informationexpressed as “nzp-resourceConfigList-r13 SEQUENCE (SIZE (1 . . . 2) or(2 . . . 8)) OF NZP-ResourceConfig-r13” of “CSI-RS-ConfigNZP-EMIMO-r13”.

Also, the CSI-RS resource #2 may correspond to“ResourceConfig-r13::=INTEGER (0 . . . 31)” configuration valueindicated in a second “NZP-ResourceConfig-r13” in the additionalconfiguration information expressed by“nzp-resourceConfigList-r13SEQUENCE (SIZE (1 . . . 2)) OFNZP-ResourceConfig-r13” of “CSI-RS-ConfigNZP-EMIMO-r13”.

Also, the CSI-RS resource #1 may correspond to “resourceConfig-r11INTEGER (0 . . . 31)” configuration value indicated in (legacy)“csi-RS-ConfigNZPld-r11” within a specific “CSI-Process-r11”configuration.

Table 9 below summarizes the case where the last legacy (default)described above corresponds to the last. In Table 9, the case of normalCP is taken as an example.

TABLE 9 Number of CSI-RS configured 4 (port), CSI-RS Normalconfiguration subframe RRC signaling CSI-RS number n_(S) (e.g.:CSI-RSresource (index) (k', l') mod2 Config. 1E) #1 6 (10, 2) 1resourceConfig-r13 INTEGER indicated in NZP- ResourceConfig-r13 #2 4 (9,5)  1 resourceConfig-r13 INTEGER indicated in NZP- ResourceConfig-r13 #32 (9, 2)  1 resourceConfig-r11 INTEGER indicated in CSI-RS-ConfigNZPld-r11

FIG. 25 is a flow chart illustrating an example of a method forreporting channel state information using aggregated CSI-RS resourcesproposed in this disclosure.

Referring to FIG. 25, the UE receives CSI-RS resource configurationinformation indicating resource configuration of a CSI-RS (ReferenceSignal) using more than 8 antenna ports, from a base station (S2510).

The CSI-RS resource configuration information may be received from theBS through high layer signaling.

In addition, the resources of the CSI-RS using more than 8 antenna portsmay be configured through the aggregation of two or more legacy CSI-RSresources.

In addition, the legacy CSI-RS resource may represent resources of theCSI-RS using more than 8 antenna ports.

In addition, the resources of the CSI-RS using more than 8 antenna portsmay be included in the same subframe.

In addition, the resources of the CSI-RS using more than 8 antenna portsmay be included in a predetermined number of consecutive symbols.

In addition, more than 8 antenna ports may be 12 ports or 16 ports.

The antenna ports equal to or less than 8 ports may be one port, twoports, four ports, or eight ports.

In addition, the aggregated two or more legacy CSI-RS resources may bethree or two resources.

The CSI-RS resource configuration information includes a plurality oflegacy CSI-RS configuration values, and the plurality of legacy CSI-RSconfiguration values may correspond to each of the aggregated two ormore legacy CSI-RS resources.

Here, the legacy CSI-RS configuration value may be a value indicating aposition of a resource element in which a legacy CSI-RS resource starts.

The specific legacy CSI-RS value included in the CSI-RS resourceconfiguration information may correspond to a legacy CSI-RS resourcehaving the lowest index among the aggregated legacy CSI-RS resources ormay correspond to legacy CSI-RS resource having the highest index.

Also, the aggregated two or more legacy CSI-RS resources maysequentially correspond to a plurality of legacy configuration valuesaligned in descending order or ascending order, starting from a lowestvalue.

Also, mapping of antenna port numbers for each resource element (RE) inthe legacy CSI-RS resource may be performed according to a predeterminedrule.

Here, the predetermined rule may be sequentially mapping by legacyCSI-RS resources or sequentially mapping by specific resource elementsin each legacy CSI-RS resource.

For example, the two or more legacy CSI-RS resources may be CSI-RSresource #1, CSI-RS resource #2, and CSI-RS resource #3.

Here, the resource elements of the CSI-RS resource #1 may be mapped tothe antenna ports 15, 16, 17 and 18, the resource elements of the CSI-RSresource #2 may be mapped to the antenna ports 19, 20, 21, and 22, andthe resource elements of the CSI-RS resource #3 may be mapped to theantenna ports 23, 24, 25, and 26.

In another example, the two or more legacy CSI-RS resources may beCSI-RS resource #1 and CSI-RS resource #2.

Here, the resource elements of the CSI-RS resource #1 may be mapped tothe antenna ports 15, 16, 17, 18, 19, 20, 21 and 22, and the resourceelements of the CSI-RS resource #2 may be mapped to the antenna ports23, 24, 25, 26, 27, 28, 29, and 30.

Thereafter, the UE receives a CSI-RS using more than eight ports fromthe BS on the basis of the received CSI-RS resource configurationinformation (S2520).

Thereafter, the UE measures channel state information (CSI) based on thereceived CSI-RS (S2530).

Thereafter, the UE reports the measured CSI to the BS (S2540).

In addition to the above-mentioned method, to which of ‘CSI referencesignal configuration’ numbers the legacy (default) CSI-RS resourcecorresponds, or the like, may be defined in a different form, and suchsimilar modifications may be understood to be included in the scope ofthe present invention.

The above-mentioned methods prevent a problem in that a continuousCSI-RS resource ID is not assigned in the process of reassigning CSI-RSresource IDs when an event such as reconfiguration occurs by CSI-RSresource IDs in RRC signaling.

Also, it is possible to apply the antenna port numbering based on the‘CSI reference signal configuration’ numbers actually indicated amongthe CSI-RS resources effectively configured for the UE through thecorresponding methods.

In this operation, preferably, it is assumed that the new CSI-RS pattern(or new CSI-RS resource) always performs multiple CSI-RS resourceaggregation in the same subframe.

The reason for this is to minimize phase drift and the like.

In this case, it may be assumed that the ‘CSI reference signalconfiguration’ numbers are not repeatedly allocated among Y number ofCSI-RS resources.

However, if the Y number of CSI-RS resources may be set over multiplesubframes, two or more CSI-RS resources having the same ‘CSI referencesignal configuration’ number may be configured.

In this case, a method of determining a secondary priority rule inascending (or descending) order of the CSI-RS resource IDs on the RRCsignaling may be considered.

General Device to which Present Invention May be Applied

FIG. 26 is a block diagram of a wireless communication device accordingto an embodiment of the present invention.

Referring to FIG. 26, a wireless communication system includes a basestation (BS) (or eNB) 2610 and a plurality of terminals (or UEs) 2620located within coverage of the BS 2610

The eNB 2410 includes a processor 2411, a memory 2412, and a radiofrequency (RF) unit 2413. The processor 2411 implements functions,processes and/or methods proposed in FIGS. 1 through 29. Layers of radiointerface protocols may be implemented by the processor 2411. The memory2412 may be connected to the processor 2411 to store various types ofinformation for driving the processor 2411. The RF unit 2413 may beconnected to the processor 2411 to transmit and/or receive a wirelesssignal.

The UE 2420 includes a processor 2421, a memory 2422, and a radiofrequency (RF) unit 2423. The processor 2421 implements functions,processes and/or methods proposed in above-described embodiments. Layersof radio interface protocols may be implemented by the processor 2421.The memory 2422 may be connected to the processor 2421 to store varioustypes of information for driving the processor 2421. The RF unit 2423may be connected to the processor 2421 to transmit and/or receive awireless signal.

The memory 2412 or 2422 may be present within or outside of theprocessor 2411 or 2421 and may be connected to the processor 2411 or2421 through various well known units. Also, the eNB 2410 and/or the UE2420 may have a single antenna or multiple antennas.

The aforementioned embodiments are achieved by combination of structuralelements and features of the present invention in a predeterminedmanner. Each of the structural elements or features should be consideredselectively unless specified separately. Each of the structural elementsor features may be carried out without being combined with otherstructural elements or features. Also, some structural elements and/orfeatures may be combined with one another to constitute the embodimentsof the present invention. The order of operations described in theembodiments of the present invention may be changed. Some structuralelements or features of one embodiment may be included in anotherembodiment, or may be replaced with corresponding structural elements orfeatures of another embodiment. Moreover, it will be apparent that someclaims referring to specific claims may be combined with another claimsreferring to the other claims other than the specific claims toconstitute the embodiment or add new claims by means of amendment afterthe application is filed.

An embodiment of the present invention may be implemented by variousmeans, for example, hardware, firmware, software or a combination ofthem. In the case of implementations by hardware, an embodiment of thepresent invention may be implemented using one or moreApplication-Specific Integrated Circuits (ASICs), Digital SignalProcessors (DSPs), Digital Signal Processing Devices (DSPDs),Programmable Logic Devices (PLDs), Field Programmable Gate Arrays(FPGAs), processors, controllers, microcontrollers and/ormicroprocessors.

In the case of implementations by firmware or software, an embodiment ofthe present invention may be implemented in the form of a module,procedure, or function for performing the aforementioned functions oroperations. Software code may be stored in the memory and driven by theprocessor. The memory may be placed inside or outside the processor, andmay exchange data with the processor through a variety of known means.

It is evident to those skilled in the art that the present invention maybe materialized in other specific forms without departing from theessential characteristics of the present invention. Accordingly, thedetailed description should not be construed as being limitative fromall aspects, but should be construed as being illustrative. The scope ofthe present invention should be determined by reasonable analysis of theattached claims, and all changes within the equivalent range of thepresent invention are included in the scope of the present invention.

The method for reporting channel state information in a wirelesscommunication system of the present invention has been described on thebasis of the example applied to the 3GPP LTE/LTE-A system, but thepresent invention may also be applied to various wireless communicationsystems other than the 3GPP/LTE/LTE-A system.

What is claimed is:
 1. A method for receiving, by a user equipment (UE),a channel state information reference signal (CSI-RS) in a wirelesscommunication system, the method comprising: receiving, from a basestation, CSI-RS resource configuration information related to anumbering for a plurality of CSI-RS resources through a radio resourcecontrol (RRC) signaling, wherein the CSI-RS resource configurationinformation includes first CSI-RS configuration information and at leastone second CSI-RS configuration information; and determining numbers forthe plurality of CSI-RS resources based on the received CSI-RS resourceconfiguration, wherein a specific CSI-RS resource among the plurality ofCSI-RS resources corresponds to a value configured in the first CSI-RSconfiguration information, and at least one CSI-RS resource except thespecific CSI-RS resource among the plurality of CSI-RS resourcescorresponds to a value configured in the second CSI-RS configurationinformation, and wherein the specific CSI-RS resource is a CSI-RSresource related to a lowest number among the plurality of CSI-RSresources.
 2. The method of claim 1, wherein the plurality of CSI-RSresources are aggregated to obtain a total number of antenna ports forthe CSI-RS using more than eight antenna ports.
 3. The method of claim1, wherein the at least one CSI-RS resource sequentially corresponds tovalues of entries configured in the second CSI-RS configurationinformation.
 4. The method of claim 3, wherein a k-th CSI-RS resource,which is a CSI-RS resource of a specific order, of the at least oneCSI-RS resource corresponds to a value of a k-th entry, which is anentry of a specific order, configured in the second CSI-RS configurationinformation.
 5. The method of claim 1, wherein the first CSI-RSconfiguration information is resourceConfig-r11 related to CSI-RSconfiguration indicated by csi-RS-ConfigNZPld-r11 used to identify theCSI-RS resource configuration, and the second CSI-RS configurationinformation is nzp-resourceConfigList-r13 related to CSI-RS resource. 6.The method of claim 1, further comprising: determining numbers for thetotal antenna ports using CSI-RS resource number information and CSI-RSresource antenna port number information.
 7. The method of claim 1,wherein the plurality of CSI-RS resources are included in a samesubframe.
 8. A user equipment (UE) for receiving a channel stateinformation reference signal (CSI-RS) in a wireless communicationsystem, the UE comprising: a radio frequency (RF) module transmittingand receiving a radio signal; and a processor functionally connected tothe RF module and controlling the UE, wherein the processor isconfigured to: receive, from a base station, CSI-RS resourceconfiguration information related to a numbering for a plurality ofCSI-RS resources through a radio resource control (RRC) signaling,wherein the CSI-RS resource configuration information includes firstCSI-RS configuration information and at least one second CSI-RSconfiguration information, and determine numbers for the plurality ofCSI-RS resources based on the received CSI-RS resource configuration,wherein a specific CSI-RS resource among the plurality of CSI-RSresources corresponds to a value configured in the first CSI-RSconfiguration information, and at least one CSI-RS resource except thespecific CSI-RS resource among the plurality of CSI-RS resourcescorresponds to a value configured in the second CSI-RS configurationinformation, and wherein the specific CSI-RS resource is a CSI-RSresource related to a lowest number among the plurality of CSI-RSresources.
 9. The UE of claim 8, wherein the plurality of CSI-RSresources are aggregated to obtain a total number of antenna ports forthe CSI-RS using more than eight antenna ports.
 10. The UE of claim 8,wherein the at least one CSI-RS resource sequentially corresponds tovalues of entries configured in the second CSI-RS configurationinformation.
 11. The UE of claim 10, wherein a k-th CSI-RS resource,which is a CSI-RS resource of a specific order, of the at least oneCSI-RS resource corresponds to a value of a k-th entry, which is anentry of a specific order, configured in the second CSI-RS configurationinformation.
 12. The UE of claim 8, wherein the first CSI-RSconfiguration information is resourceConfig-r11 related to a CSI-RSconfiguration indicated by csi-RS-ConfigNZPld-r11 used to identify theCSI-RS resource configuration, and the second CSI-RS configurationinformation is nzp-resourceConfigList-r13 related to a CSI-RS resource.13. The UE of claim 8, wherein the processor determines numbers for thetotal antenna ports using CSI-RS resource number information and CSI-RSresource antenna port number information.
 14. The UE of claim 8, whereinthe plurality of CSI-RS resources are included in a same subframe.